ANALYSIS OF ALTERNATIVES non-confidential report
Legal name of applicant(s): LANXESS Deutschland GmbH in its legal capacity as Only Representative of LANXESS CISA (Pty) Ltd.; Atotech Deutschland GmbH; Aviall Services Inc.; BONDEX TRADING LTD in its legal capacity as Only Representative of Aktyubinsk Chromium Chemicals Plant, Kazakhstan; CROMITAL S.P.A. in its legal capacity as Only Representative of Soda Sanayii A.S.; Elementis Chromium LLP in its legal capacity as Only Representative of Elementis Chromium Inc; Enthone GmbH.
Submitted by: LANXESS Deutschland GmbH in its legal capacity as Only Representative of LANXESS CISA (Pty) Ltd. Substance: Chromium trioxide EC No: 215-607-8, CAS No: 1333-82-0
Use title: Surface treatment (except ETP) for applications in various industry sectors namely architectural, automotive, metal manufacturing and finishing, and general engineering
Use number: 5
i Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Disclaimer
This document shall not be construed as expressly or implicitly granting a license or any rights to use related to any content or information contained therein. In no event shall applicant be liable in this respect for any damage arising out or in connection with access, use of any content or information contained therein despite the lack of approval to do so.
ii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
CONTENTS
1. SUMMARY ...... 1 2. INTRODUCTION ...... 9 2.1. Substance ...... 9 2.2. Uses of chromium trioxide ...... 9 2.3. Purpose and benefits of chromium trioxide ...... 9 3. ANALYSIS OF SUBSTANCE FUNCTION...... 11 3.1. Use ...... 11 3.2. Surface treatment processes ...... 13 3.2.1. Pre-treatment processes ...... 15 3.2.1.1 Functional cleaning ...... 15 3.2.1.2 Pickling and etching ...... 16 3.2.1.3 Deoxidising ...... 16 3.2.1.4 Stripping ...... 17 3.2.2. Main surface treatment processes...... 17 3.2.2.1 Chemical conversion coating (including phosphate conversion coating: phosphating) ...... 17 3.2.2.2 Chromic acid anodising (CAA) ...... 18 3.2.2.3 Electrolytic chromium coated steel (ECCS) / tin-free steel (TFS) ...... 19 3.2.2.4 Grain-oriented electrical steel (GOES) insulation ...... 20 3.2.2.5 Passivation of copper foils ...... 21 3.2.3. Post-treatment processes ...... 22 3.2.3.1 Sealing after anodizing ...... 22 3.3. Key chromium trioxide functionalities in surface treatment processes ...... 23 3.3.1. Pre-treatments - key functionalities ...... 23 3.3.1.1 Functional cleaning, pickling, etching ...... 24 3.3.1.2 Deoxidising ...... 24 3.3.1.3 Stripping of inorganic finishes ...... 24 3.3.1.4 Chemical stripping of organic coatings (e.g. primers, topcoats and specialty coatings) ...... 25 3.3.2. Key functionalities of chromium trioxide-based main processes & post-treatments ...... 25 3.3.3. Sector specific key functionalities ...... 27 3.3.3.1 Architectural sector ...... 27 3.3.3.2 Automotive sector ...... 28 3.3.3.3 Packaging industry ...... 28 3.3.3.4 General engineering ...... 29 4. ANNUAL TONNAGE...... 32 4.1. Annual tonnage band of chromium trioxide ...... 32 5. GENERAL OVERVIEW ON THE SPECIFIC APPROVAL PROCESS IN THE DIFFERENT INDUSTRY SECTORS ...... 33 5.1. Architectural ...... 33 5.2. Automotive sector specific approval process ...... 35 5.2.1. Current production parts in automotive applications - general considerations...... 35 5.2.2. Current production parts - requirements for alternatives to chromium trioxide ...... 35 5.2.3. Past model service parts – general considerations ...... 36 5.2.4. Past model service parts – requirements for alternatives to chromium trioxide ...... 37 5.3. Packaging and food contact ...... 38 5.4. General engineering ...... 44 6. IDENTIFICATION OF POSSIBLE ALTERNATIVES ...... 45 6.1. Description of efforts made to identify possible alternatives ...... 45 6.1.1. Research and development ...... 45 6.1.2. Data searches ...... 46 6.2. Consultations ...... 46 6.3. List of possible alternatives ...... 47 7. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES ...... 48 7.1. Main processes & post-treatments ...... 48 CATEGORY 1 ALTERNATIVES ...... 48 7.1.1. ALTERNATIVE 1: Acidic surface treatments ...... 48 7.1.1.1 Substance ID and properties ...... 48 7.1.1.2 Technical feasibility ...... 49
iii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.1.2.1Architectural industry ...... 49 7.1.1.2.Automotive sector ...... 51 7.1.1.3 Economic feasibility ...... 52 7.1.1.4 Reduction of overall risk due to transition to the alternative ...... 52 7.1.1.5 Availability ...... 52 7.1.1.6 Conclusion on suitability and availability for Acidic surface treatments ...... 52 7.1.2. Alternative 2: Cr(III)-based surface treatments ...... 53 7.1.2.1 Substance ID and properties ...... 53 7.1.2.2 Technical feasibility ...... 53 7.1.2.2.1Architectural industry ...... 53 7.1.2.2.2Automotive ...... 55 7.1.2.2.3General engineering ...... 55 7.1.2.3 Economic feasibility ...... 57 7.1.2.4 Reduction of overall risk due to transition to the alternative ...... 57 7.1.2.5 Availability ...... 57 7.1.2.6 Conclusion on suitability and availability for Cr(III)-based processes ...... 58 7.1.3. ALTERNATIVE 3: Silane/Siloxane and sol-gel coatings ...... 59 7.1.3.1 Substance ID and properties ...... 59 7.1.3.2 Technical feasibility ...... 60 7.1.3.2.1Architectural industry ...... 60 7.1.3.2.2Automotive sector ...... 61 7.1.3.3 Economic feasibility ...... 62 7.1.3.4 Reduction of overall risk due to transition to the alternative ...... 62 7.1.3.5 Availability ...... 62 7.1.3.6 Conclusion on suitability and availability for Silane or siloxane-based sol-gel processes ...... 63 7.1.4. ALTERNATIVE 4: Manganese-based processes ...... 63 7.1.4.1 Substance ID and properties ...... 63 7.1.4.2 Technical feasibility ...... 64 7.1.4.2.1Architectural industry ...... 64 7.1.4.3 Economic feasibility ...... 64 7.1.4.4 Reduction of overall risk due to transition to the alternative ...... 64 7.1.4.5 Availability ...... 65 7.1.4.6 Conclusion on suitability and availability for manganese-based processes ...... 65 7.1.5. ALTERNATIVE 5: Molybdates and Molybdenum-based processes...... 65 7.1.5.1 Substance ID and properties ...... 65 7.1.5.2 Technical feasibility ...... 65 7.1.5.2.1Architectural industry ...... 65 7.1.5.3 Economic feasibility ...... 66 7.1.5.4 Reduction of overall risk due to transition to the alternative ...... 66 7.1.5.5 Availability ...... 66 7.1.5.6 Conclusion on suitability and availability for molybdates and molybdenum-based processes ...... 67 7.1.6. ALTERNATIVE 6: Organometallics (Zr- and Ti-based products) ...... 67 7.1.6.1 Substance ID and properties ...... 67 7.1.6.2 Technical feasibility ...... 67 7.1.6.2.1Architectural industry ...... 68 7.1.6.2.2General engineering ...... 69 7.1.6.3 Economic feasibility ...... 70 7.1.6.4 Reduction of overall risk due to transition to the alternative ...... 70 7.1.6.5 Availability ...... 70 7.1.6.6 Conclusion on suitability and availability for fluorotitanic- and fluorozirconic-based products ...... 71 7.1.7. ALTERNATIVE 7: Benzotriazole-based processes, e.g. 5-methyl-1H-benzotriazol ...... 71 7.1.7.1 Substance ID and Properties ...... 71 7.1.7.2 Technical feasibility ...... 71 7.1.7.3 Economic feasibility ...... 72 7.1.7.4 Reduction of the overall risk due to transition to the alternative ...... 72 7.1.7.5 Availability ...... 72 7.1.7.6 Conclusion on suitability and availability for benzotriazole-based processes...... 72 7.1.8. ALTERNATIVE 8: Physical vapour deposition (PVD) ...... 72 7.1.8.1 Substance ID and properties ...... 73 7.1.8.2 Technical feasibility ...... 73 iv Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.8.3 Economic feasibility ...... 74 7.1.8.4 Reduction of overall risk due to transition to the alternative ...... 75 7.1.8.5 Availability ...... 75 7.1.8.6 Conclusion on suitability and availability for PVD...... 75 7.1.9. ALTERNATIVE 9: Other oxide-based coatings ...... 75 7.1.9.1 Substance ID and properties ...... 75 7.1.9.2 Technical feasibility ...... 76 7.1.9.3 Economic feasibility ...... 77 7.1.9.4 Reduction of overall risk due to transition to the alternative ...... 77 7.1.9.5 Availability ...... 77 7.1.9.6 Conclusion on suitability and availability for other oxide-based coatings ...... 77 7.1.10. ALTERNATIVE 10: Low tin steel (LTS) ...... 77 7.1.10.1 Low tin steel with and without Cr(VI)-free liquid phase conversion coating ...... 78 7.1.10.1.1Substance ID and properties ...... 78 7.1.10.1.2Technical feasibility ...... 78 7.1.10.1.3Economic feasibility ...... 80 7.1.10.1.4Reduction of overall risk due to transition to the alternative ...... 80 7.1.10.1.5Availability ...... 80 7.1.10.1.6Conclusion on suitability and availability for LTS ...... 80 7.1.10.2 LTS with silane/siloxane Coatings (CVD) ...... 81 7.1.10.2.1Substance ID and properties ...... 81 7.1.10.2.2Technical feasibility ...... 81 7.1.10.2.3Economic feasibility ...... 81 7.1.10.2.4Reduction of overall risk due to transition to the alternative ...... 82 7.1.10.2.5Availability ...... 82 7.1.10.2.6Conclusion on suitability and availability for LTS with silane/siloxane coatings ...... 82 7.2. Pre-treatments ...... 82 7.2.1. Inorganic acids ...... 82 7.2.1.1 Substance ID and properties ...... 82 7.2.1.2 Technical feasibility ...... 82 7.2.1.3 Economic feasibility ...... 86 7.2.1.4 Reduction of overall risk due to transition to the alternative ...... 86 7.2.1.5 Availability ...... 87 7.2.1.6 Conclusion on suitability and availability for inorganic acids ...... 87 7.2.2. Pickling/Etching of copper ...... 87 7.2.2.1 Substance ID and properties ...... 87 7.2.2.2 Technical feasibility ...... 88 7.2.2.3 Economic feasibility ...... 88 7.2.2.4 Reduction of overall risk due to transition to the alternative ...... 88 7.2.2.5 Availability ...... 88 7.2.2.6 Conclusion on suitability and availability for pickling/etching of copper ...... 89 8. OVERALL CONCLUSIONS ON SUITABILITYAND AVAILABILITY OF POSSIBLE ALTERNATIVES ... 90 APPENDIX 1 – INITIAL LIST OF POTENTIAL ALTERNATIVES TO CHROMIUM TRIOXIDE-CONTAINING SURFACE TREATMENTS ...... 94 APPENDIX 2 – GENERAL INFORMATION AND THE RISK FOR HUMAN HEALTH AND THE ENVIRONMENT FOR RELEVANT SUBSTANCES ...... 96 APPENDIX 2.1: MAIN PROCESSES AND POST-TREATMENTS ...... 96 APPENDIX 2.2: PRE-TREATMENTS ...... 110 APPENDIX 2.3: SOURCES OF INFORMATION ...... 116
v Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
List of Figures:
Figure 1: Surface Treatment Processes steps where chromates might be involved ...... 3 Figure 2: Surface treatment processes steps where chromium trioxide might be involved ...... 13 Figure 3: Schematic anodic coating after acidic anodising (Hao & Cheng, 2002) ...... 19 Figure 4: TFS composition illustrated with a schematic cross section. (www.jfe-steel.co.jp) ...... 19 Figure 5: Tin plate cross section (www.jfe-steel.co.jp) ...... 20 Figure 6: Illustration of non-oriented and grain-oriented electrical steel (http://www.thyssenkrupp.com) ...... 20 Figure 7: Rolled copper foil treatment process. (Lu D., Wong CP., Materials for Advanced Packaging, 2009, p.290, Fig. 8.11) ...... 21 Figure 8: Electrodeposited copper manufacturing process (Rogers Corporation, Copper Foils for High Frequency Circuit Materials, 2014) ...... 22 Figure 9: Car dismantled into constituent parts (Volkswagen AG, 2013) (left). Principal engine parts of a car (HubPages, undated) (right)...... 35 Figure 10: Typical life-time of a car model with start in production in 2018 compared with a four years period until sunset date (ACEA, 2013) ...... 36 Figure 11: EU passenger car fleet (%s hare by age in 2010). Note: Information from 12 EU Member States where information was available (ACEA, 2013)...... 37 Figure 12: Overall lacquer adhesion performance of IPSA materials expressed as “defect rate” on a scale from 0% (excellent) to 100% (very poor) (Marmann, 2013)...... 79
vi Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
List of Tables
Table 1: Examples of applications of surface treatment using chromium trioxide ...... 2 Table 2: Summary of Findings of AoA (x marks technical failure, (x) marks failure not for all applications...... 7 Table 3: Substance of this analysis of alternatives...... 9 Table 4: Overview of surface treatment processes indicating most important application methods, purpose, as well as example products. This is not intended to be an exhaustive list...... 14 Table 5: Key requirements within the architectural sector ...... 27 Table 6: Key requirements within the automotive sector ...... 28 Table 7: Key requirements within the Packaging industry...... 28 Table 8: Key requirements within the steel processing sector ...... 29 Table 9: List of main treatment alternatives categorised (Category 1, highlighted in yellow; Category 2, highlighted in red) ...... 47 Table 10: List of pre-treatment alternatives categorised...... 47 Table 11: Overview on the acids used in the different surfaces treatment processes ...... 49 Table 12: Sector specific overview on chromium trioxide-based surface treatments processes where Cr(III)-based technics are evaluated ...... 53 Table 13: Chromium trioxide-based surface treatments processes where sol-gel coatings may be an alternative ...... 60 Table 14: Chromium trioxide-based surface treatments processes where manganese-based products may be an alternative ...... 64 Table 15: Chromium trioxide-based surface treatments where molybdate-based processes may be an alternative .... 65 Table 16: Chromium trioxide-based surface treatments where fluorotitanic and fluorozirconic-based products may be an alternative ...... 67 Table 17: Chromium trioxide-based surface treatments where PVD may be an alternative...... 73 Table 18: Material properties of typical PVD coatings (Legg K., 2003a) ...... 73 Table 19: Sector specific overview on chromium trioxide-based surface treatments processes where other oxide-based coatings are evaluated ...... 76 Table 20: Overview on potential alternatives to Electrolytic Chromium Coated Steel (ECCS) for the packaging sector...... 77 Table 21: Overview on the replacement substances used in the different pre-treatment processes ...... 83 Table 22: Overview on the replacement substances used in the different pre-treatment processes ...... 88 Table 23: Summary of Findings of AoA (x marks technical failure, (x) marks failure not for all applications) ...... 91
vii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Abbreviations ACF Airbus Chromate-Free Al Aluminium Acute Tox. Acute Toxicity AMMTIAC Advanced Materials, Manufacturing, and Testing Information Analysis Center Asp. Tox. Aspiration hazard ASTM American Society for Testing Materials AoA Analysis of Alternatives Aquatic Acute Hazardous to the aquatic environment Aquatic chronic Hazardous to the aquatic environment CAA Chromic Acid Anodizing Carc. Carcinogenicity CAS unique numerical identifier assigned by Chemical Abstracts Service (CAS number) CASS test Copper Accelerated Salt spray test CCC Chemical conversion coatings Cd Cadmium Cr Chromium Cr(0) Elementary Chromium Cr(III) Trivalent Chromium Cr(VI) Hexavalent Chromium CRES Corrosion resistant stainless steel CSR Chemical Safety Report CTAC Chromium Trioxide REACH Authorization Consortium EC unique numerical identifier of the European Community (EC number) ECCS Electrolytic Chromium Coated Steel EFSA European Food Safety Authority EG Electro-galvanized steel EMI Electromagnetic Interference EN European Norm EPA Environmental Protection Agency ESA European Space Agency viii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
EU European Union Eye Dam. Serious ey damage Eye Irrit. Eye irritation FDA US Food and Drugs Administration Flam. Liq. Flammable liquid Flam.sol. Flammable solid GSB Quality Association for the Piecework Coating of Building Components (Gütegemeinschaft für die Stückbeschichtung von Bauteilen e.V.) HDG Hot dip galvanized steel HITEA Highly Innovative Technology Enablers for Aerospace HV Vickers Hardness ISO International Organization for Standardization Me Metal Met. Corr. Substance or mixture corrosive to metals Mg Magnesium Mil-DTL United States Military Standard MoCC Molybdate-based conversion coatings MRL Manufacturing Readiness Level SDS Safety Data Sheet Muta. Germ cell mutagenicity NASA National Aeronautics and Space Administration Ni Nickel OEM Original Equipment Manufacturer Ox. Liq. Oxidising liquid Ox. Sol. Oxidising solid PSA Phosphoric Sulphuric Acid Anodizing PVD Physical Vapour Deposition REACH Registration, Evaluation, Authorisation and Restriction of Chemicals R&D Research and Development Repr. Reproductive toxicity Resp. Sens. Respiratory SAA Sulphuric Acid Anodizing
ix Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
SEA Socio Economic Analysis Skin. corr. Skin corrosion Skin. Sens. Skin sensitisation Skin irrit. Skin irritation Sn Tin SST Salt Spray Test STOT RE Specific target organ toxicity, repeated exposure STOT SE Specific target organ toxicity, single exposure SVHC Substance of Very High Concern Ti Titanium TRL Technology Readiness Level US United States VTMS Vinyl trimethoxysilane
x Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Glossary
Term Definition
The ability of a material to spontaneously repair small amounts of chemical or mechanical damage that exposes areas of metal without any surface Active corrosion inhibition protection (“self-healing properties”). This functionality is advantageous and enhances service life duration of parts. Parameter describes the tendency of dissimilar particles or surfaces to cling Adhesion promotion to one another (for example adhesion of coating to substrate, adhesion of paint to coating and/or substrate). This terms comprises civil and military applications of aviation and space Aerospace industry. Electrolytic oxidation process in which the surface of a metal, when anodic, Anodizing is converted to a coating having desirable protective or functional properties. Chromic acid anodizing is one example of anodizing. Typical method for surface treatment of parts. May also be referred to as Bath dipping or immersion. None-bath methods include wiping, spraying, pouring and pen application. The process where two parts are joint together by means of a bonding Bonding material; an adhesive sometimes in combination with a bonding primer and a conversion or anodizing treatment Alternative considered promising, where considerable R&D efforts have Category 1 alternative been carried out within the different industry sectors. Alternative with clear technical limitations which may only be suitable for Category 2 alternative niche applications and not as a general alternative. Alternative which has been screened out at an early stage of the Analysis Category 3 alternative of Alternatives and which is not applicable for the use defined here. Parameter is defined as the ability of solid materials to resist damage by Chemical resistance chemical exposure. When brought in contact with water, chromium trioxide forms two acids and several oligomers: chromic acid, dichromic acid, and oligomers of Chromic acid chromic acid and dichromic acid. For the purpose of this document the terms chromic acid is synonymous with a mixture containing chromium trioxide and water. This is intended to be in line with ECHA Q&A #805. Surface preparation for subsequent processing including removal of dirt Cleaning and oil. The term has some overlap with the definitions of pickling, descaling and deoxidising. A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be Coating decorative, functional, or both. A coating may be a paint, a lacquer or a metal (e.g. functional chrome, cadmium coating, zinc-nickel coating) or an inorganic substance. Chemical process applied to a substrate producing a superficial layer containing a compound of the substrate metal and an anion of an Conversion coating environment. Note that within the surface finishing industry a conversion coating is sometimes referred to as a passive coating or passivation.
Corrosion protection Means applied to the metal surface to prevent or interrupt oxidation of the metal part leading to loss of material. This can be a metal conversion
xi Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Term Definition coating or anodizing, a pre-treatment, paint, water repellent coating, sealant, liquid, adhesive or bonding material. The corrosion protection provides corrosion resistance to the surface. Deoxidising is a pre-treatment step required to activate the surface prior to further processing i.e. to remove surface oxides. The term deoxidising is Deoxidising often used interchangeably with pickling. Very little metal is removed during deoxidising. Surface preparation for subsequent processing including removal of scale Descaling and oxides. The term has some overlap with the definitions of pickling, cleaning and deoxidising. Removal of residue that is often left over from etching processes. Desmutting Desmutting is often grouped with cleaning, deoxidizing or pickling. Chromium coated steel is a sheet or strip of steel electrolytically coated Electrolytic chromium coated with a layer of chrome thinner than a micron. It is also known as TFS (Tin steel Free Steel). Process that changes surface as well as removes material. This term has Etching significant overlap with the term pickling. Grain oriented steel A coating that is applied to steel strip or steel sheet for the manufacture of insulation electrical apparatus. After having passed qualification and certification, the third step is to Implementation implement or industrialise the qualified material or process in all relevant activities and operations of production, maintenance and the supply chain. In-service evaluations are common practice to validate results obtained in In-service evaluation the laboratory to determine correlation between e.g. accelerated corrosion testing and when used in operating scale. The purpose of the surface treatment is primarily for, but not limited to, corrosion protection. The main treatment occurs after the pre-treatment and before the post treatment. Examples include conversion coating, anodizing Main treatment and passivation of stainless steel. Sometimes conversion coating and anodizing are followed by painting; in which case these can be regarded as the pre-treatment and the painting as the main treatment. Process providing corrosion protection to a substrate or a coating. Note that within the surface finishing industry a passive or passivation coating is Passivation often referred to as a conversion coating. Both terms are used in this document. Chemical process applied to a substrate producing a superficial layer Passivation of copper foils containing a compound of the substrate metal and an anion of an environment for the production of printed circuit boards (PCBs) Is designed to both remove embedded iron/steel particles from stainless Passivation of stainless steel steel and oxidise the surface chromium in the alloy to augment its natural corrosion resistant passive oxide layer. Metallic coatings applied on steel (such as cadmium, zinc, zinc-nickel, or Passivation of metallic aluminium) need to be passivated for corrosion protection. Technically, this coatings kind of passivation is a conversion coating and the process is a post- treatment applied after the application of the non-chromium metal coating. A non-chromated conversion process containing metal phosphates used Phosphating mainly for some ferrous substrates and is generally used a key for subsequent painting, oiling or lubrication films. xii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Term Definition Pickling is the removal of oxides or other compounds from a metal surface by chemical or electrochemical action. The term pickling is not used consistently with the surface finishing industry and is often referred to as Pickling the following processes: cleaning, scale removal, scale conditioning, deoxidizing, etching, and passivation of stainless steel. This term has overlap with the term Etching. Post-treatment processes are performed after the main surface treatment Post-treatment process to enhance corrosion protection. Pre-treatment processes are used to remove contaminates (e.g. oil, grease, dust), oxides, scale, and previously applied coatings (e.g. electroplated Pre-treatment coatings, anodize coatings, conversion coatings, paint). The pre-treatment process must also provide chemically active surfaces for the subsequent treatment. A series of surface treatment process steps. The individual steps are not stand-alone processes. The processes work together as a system, and care Process chain should be taken not to assess without consideration of the other steps of the process. In assessing alternatives for chromates, the whole process chain has to be taken into account. OEM validation and verification that all material, components, equipment or processes have to meet or exceed the specific performance requirements Qualification which are defined in the Certification Specifications documented in technical standards or specifications. Numerous applications require an electrical conductive coating for the Resistivity respective use. Material to fill gaps or joints or to exclude the environment in order to prevent electrochemical corrosion between two parts with dissimilar Sealant material composition (metal-metal and metal-carbon composite) or crevice corrosion. This can be applied by means of spatula, extrusion, brush or spray. For a high corrosion resistance micropores of the anodized surface have to Sealing be closed by a post-treatment step (sealing after anodizing). Removal of coatings prior to rework. Differentiation based on the kind of Stripping coating removed (stripping or inorganic finishes, stripping or organic coatings). This Use includes processes that convert the surface of an active metal or coat metal surfaces by forming/incorporating a barrier film of complex Surface treatment (except chromium compounds that protects the metal from corrosion, provides a ETP) for applications in base for subsequent painting, provides a chemical polish, and/or colors the various industry sectors metal. This includes integrated process systems where chromium trioxide namely architectural, is used in a series of pre/main/post-treatments. Pre-treatment includes automotive, metal processes such as chemical polishing, stripping, dexodizing, pickling and manufacturing and finishing, etching of metals or other materials. Main-treatment includes processes and general engineering such as conversion coatings, passivation and anodizing, deposition and (hereafter referred to as other surface treatments where a chromium trioxide-based solution is used. surface treatment for Specifically, this includes continuous coil coating of steel and passivation miscellaneous sectors) (e.g. zinc plating, copper foils), but not passivation of tin-plated steel. Post- treatment includes processes such as rinsing, staining and sealing for final surface protection.
xiii Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed.
ANALYSIS OF ALTERNATIVES
1. SUMMARY This Analysis of Alternatives (AoA) forms part of the Application for Authorisation (AfA) for the use of chromium trioxide in the surface treatment of metals. The use, as defined, covers a number of surface treatment processes and steps1 that may be applied to a number of different metal substrates (e.g. aluminium, steel, zinc, copper, magnesium, titanium, alloys and composites with metallic areas). The use is also intended to cover the downstream use of chromic acid and dichromic acid (in-line with ECHA Q&A #805). Surface treatment aims to modify the surface of a substrate so that it performs better under conditions of use. Surface treatment processes using chromium trioxide typically involve immersion of the metal component in each of a series of treatment baths containing chemical solutions or rinses under specific operating conditions. Different chemicals and operating conditions are specified for individual surface treatment processes (see Figure 1) in order to effectively treat different substrates and/or confer specific performance characteristics to the treated article. The relevant surface treatment processes which the AfA covers, the characteristics of chromium trioxide and its critical functionality in each of the treatment processes are introduced at chapter 3. Surface treatment with chromium trioxide is specified in many applications across industry in order to meet strict performance criteria, also in relation to regulatory compliance and for public safety, as described further below (Table 1) and in chapter 5. The automotive, defence, marine, energy, oil & gas, electricity, building & construction, steel and non-ferrous metal, food packaging, material science, printing, paper, and many other sectors depend on chromium trioxide to meet their high requirements on products used under a broad variety of conditions. This summary aims to shortly explain why use of chromium trioxide in surface treatment is essential to the automotive, architectural, food packaging sector, general engineering and other sectors. It describes the steps and effort involved in finding and approving a replacement for chromium trioxide in these applications and evaluates potential alternatives in detail (chapter 6). Use of chromium trioxide-based surface treatment systems Chromium trioxide has been used for more than 50 years to provide surface protection to critical components and products within various industry sectors, where the products to which they are applied must operate to the highest safety standards in highly demanding environments for extended time periods. Surface treatments based on chromates including chromium trioxide have unique technical functions that confer substantial advantage over potential alternatives. These include: - Outstanding corrosion protection and prevention for nearly all metals under a wide range of conditions; - Active corrosion inhibition (self-sealing, e.g. repairing a local scratch to the surface); - Excellent adhesion properties to support application of subsequent coatings or paints; - Excellent chemical and electrical resistivity; - Enhanced wear and chemical resistance; and - Optimal layer thickness. The chemistry behind surface treatment systems and processes using chromium trioxide is complex. Surface treatment processes typically involve numerous steps, often including several important pre- treatment and post-treatment steps as well as the main treatment process itself. These steps are almost
1 See Chapter 3 for detail.
1 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
always inter-related such that they cannot be separated or individually modified without impairing the overall process or performance of the treated product. This means it is imperative to consider the surface treatment system as a whole, rather than the step involving chromium trioxide on its own, when considering alternatives for such surface treatment systems. Furthermore, components that have been surface treated with chromium trioxide typically represent just one of many critical, inter-dependent elements of a component, assembly or system. In general, chromium trioxide-based surface treatment is specified as one element of a complex system with integrated, often critical performance criteria. Compatibility with and technical performance of the overall system are primary considerations of fundamental importance during material specification. Several alternatives are being tested to substitute chromium trioxide in surface treatment applications. It is a challenge to find a substitute which meets all requirements for a product, for each use, and specific applications while also being technically and economically feasible. Many alternatives are already qualified for some applications and substrates but none of them provides all the key properties of chromium trioxide as defined in the following sections.
Table 1: Examples of applications of surface treatment using chromium trioxide
Sector Critical Functionalities Example of components
Wear and corrosion protection Shock absorbers, gas springs, steering and differential Adhesive properties components, power trains, piston rods, hydraulics, fuel injection components, piston rings, break pistons, cold roll Automotive High hardness cylinders, and bearings. Coil coated metals are used e.g. in Chemical resistance car bodies, trailer bodies, recreational vehicles, oil filter Variable coating thickness caps, wiper blade assemblies.
Architecture Corrosion protection Use of coil coated aluminium or steel in the building & building envelope, gutters, partitions, ceiling systems and a variety of construction Adhesion ancillary components. Corrosion resistance - Specialized screens Adhesion - Printed circuit boards (PCB) production General Chemical protection - Power transformers, shunt reactors, power generators - Coil engineering coated metals are used wherever the end use demands a Layer thickness high-quality painted finish on a component fabricated from Optical properties sheet metal. Corrosion resistance Food Adhesion - crown corks, twist-off caps and aerosol bottoms and tops Packaging Food safety
Use of chromium trioxide in surface treatment Chromium trioxide-based surface treatments are specified by industry because they provide superior corrosion resistance and inhibition, improved paint adhesion, low electrical contact resistance and/or enhanced wear-resistance (see Chapter 3.3). These characteristics are generally essential to the safe operation and reliability of vehicles, equipment and machinery which operate under extreme conditions. Chromium trioxide surface treatment processes and performance have been successively refined and improved as a result of many decades of research and experience in the sector, and reliable data is available to support their performance. While corrosion cannot be totally prevented, despite the highly advanced nature of chromium trioxide-based coating systems in place today, there is also extensive
2 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES experience, amassed over decades, on the appearance and impact of corrosion to support its effective management in these systems. On the other hand, while several potential alternatives to chromium trioxide are being investigated for different processes, substrates and treatment steps, results so far do not support reliable conclusions regarding their performance as part of such complex systems, in demanding environments and real-world situations. These potential alternatives do not support all the properties of chromium trioxide-based surface treatment systems, and their long-term performance can currently only be estimated. Decreased performance would necessitate shorter inspection intervals, with a substantial impact on associated maintenance costs.
Use Description Surface Treatment of Metal Parts
Pre-Treatment Treatment Post Treatment • Cleaning • Conversion Coating • Sealing after Anodizing • Pickling/Etching • Anodizing • Passivation • Deoxidising
Figure 1: Surface Treatment Processes steps where chromates might be involved Figure 1 provides an overview of the applications included in the application for authorisation according to the process steps. These steps are almost always inter-related such that they cannot be separated or individually modified without impairing the overall process or performance of the treated product.
Considerations affecting availability of potential alternatives Architecture: Qualicoat is an organisation that seeks to promote the quality of coating on aluminium and its alloys for architectural applications through the use of a product certification scheme and quality label system. It defines comprehensive quality requirements and monitors compliance of licensed plants worldwide against these requirements. This provides assurance to purchasers of coated aluminium that the product they receive delivers long-term value and consistent quality that is measurable against technical specifications for plants and equipment, coating materials and finished products. All requirements in the specifications must be met before a quality label can be granted. The Qualicoat specifications and approval procedures for products are based on a variety of accelerated laboratory tests and limited period outdoor exposure testing. The most demanding tests are the acetic acid salt spray testing and the outdoor exposure testing. Additionally, stringent mechanical adhesion tests have to be passed. National associations are licensed to inspect manufacturing plants and issue certificates. Licensed coating plants that fail to meet the requirements lose their licence. The aluminium coating industry confirms that customers are very demanding with regard to performance of Cr(VI)-free alternative coating products. There is an increasing demand for approval and certification by the Quality Association for the Piecework Coating of Building Components (GSB) whose testing and approval regime is even more stringent than those of Qualicoat and includes outdoor exposure testing and evaluation for 36 months at an industrial site under harsh environmental (sea-side) conditions.
3 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Manufacturers in the building sector generally have to give a 25 years lasting guarantee for the products. Indeed, at the current stage, the Cr(VI)-free alternatives have not been tested for such a long lifetime. Coatings manufacturers currently perform extensive tests on alternative products to meet the requirements of the quality label. However, these data are from laboratory or short-term outdoor testing and can therefore not be relied on by manufacturers and the market to substantiate the corrosion resistance of a specific alternative product as long as long-term field tests have not been concluded. There have indeed been many costly field failures with Cr(VI)-free alternatives reported over recent years. In the end, the only true indicator of the corrosion performance in salt air and humidity is long-term exposure data for decades in real-world environments. Automotive: Chromium trioxide is used by automobile supply chains in processes including passivation to manufacture several thousand parts of chromium-treated parts per vehicle manufacturer. Parts cover a wide range of applications, in vehicle models with a production period of 7-10 years. Introducing new materials into the automotive market is a complex process, involving multiple phases and checks. Safety is the main driver for this. Chromium trioxide-based surface treatment of parts offers superior performance in terms of corrosion resistance, hardness, layer thickness, and adhesive strength. Potential alternatives in the automotive industry must be able to cover all of these requirements. As a drop-in replacement is not available, careful testing and evaluation of potential alternatives’ functional behaviour is needed. Current testing procedures in the automotive sector include laboratory tests, summer and winter tests, and continuous-operation tests. Thorough evaluation of possible alternatives is crucial to avoid failures in the field / daily application. As well as consequences for safety, failure could result in expensive and brand damaging product recalls. In the case of replacing chromium trioxide, all affected components must be revalidated using alternative materials. Substance substitution may cause change of function geometry, thermal durability and leads to unexpected impacts on related parts. Even though the automobile industry is highly experienced in material testing procedures, the validation and testing of alternatives will require several years due to the sheer number of parts involved. In addition, performance of potential alternatives must be tested under conditions of large scale production. Type approval is the confirmation that production samples of a design will meet specified performance standards. The specification of the product is recorded and only that specification is approved. Within the European automotive industry, two systems of type approval have been in existence for over 20 years. Automotive EC Directives and UN Regulations require third party approval - testing, certification and production conformity assessment by an independent body. A stepwise introduction of alternative technologies in new type-approved models is foreseen by the automotive industry due to the magnitude of the change and impact on the industry. To make sure production volumes of vehicles are not affected, sufficient capacities for the production of alternative coatings in Europe must be confidently in place. Furthermore, due to the high complexity of the supply chain in the automotive industry, tracking down chromium trioxide depending parts is a time- consuming and complicated task. Assembly of vehicles is carried out across a complex network of manufacturing plants, with an average number of 1500-4500 Original Equipment Manufacturer (OEM) suppliers, each of whom have an average of 500-1500 suppliers themselves. With regard to both the highly complex nature of supply chains in the automotive industry and the lifetime of vehicles, planning reliability is crucial. Realistically, changes to a vehicle model can only
4 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES be made in a certain period of time, which decreases rapidly after type-approval by a certified body in the early stages of new model development. The majority of European cars are removed from the fleet after 13 - 15 years. About 36% of the European Union (EU) passenger car fleet of 224 million vehicles - approximately 80 million cars - are older than 10 years, further underlining the need for an efficient supply of past model service parts beyond the end of serial production. Commonly, past model service parts are provided for vehicles that have been out of production for more than 20 years. A minimum of ten years availability of spare parts must be assured to comply with legislation in some EU Member States. Surface treatment applications that use chromium trioxide are required for spare parts. To make sure that possible alternatives are interchangeable with original spare parts, a complete new type-approval is necessary. The identification of possible alternatives and the careful validation of their functionalities is a labour/time intensive process that will certainly take several years. According to the European Automobile Manufacturer Association (ACEA), the development of suitable alternatives for chromium trioxide-based processes within this use will require a time period of at least 5 years followed by industrialization of the technique and implementation in the supply chain. The minimum time-frame required is 7 years after the sunset date. General engineering and others: Surface treatments using chromium trioxide are used in thousands of different complex equipment, vehicles and machines within the scope of general engineering. This includes agricultural machinery as well as trucks and forklifts, transistors, bearings, and steel coil. Surface treatment with chromium trioxide is necessary to ensure critical parts do not corrode or wear and can withstand heavy duty operations over long periods of operation. The steel processing industry utilises several surface treatment applications requiring chromium trioxide. Engineering coatings are produced to enhance the properties of the substrate. It is the functional surface coating which enables a product to fulfill its function more effectively. Chromate conversion coating is applied on various substrates and coatings to enhance corrosion resistance and paint adhesion. Optical properties also play a crucial role as customers in the current highly competitive market are very sensitive to aesthetic aspects. As of 2012, the turnover of the European coil coating industry was estimated to be € 5.5 billion with an output of 1,240 million m2 of coated metal. Chromium trioxide is used as a component of the final coating on grain oriented electrical steels. These steels are produced mainly for electrical transformers for which they offer vital properties. Chromium trioxide is applied in the insulation layer which has to be resistant to corrosion and chemicals such as transformer oils and to withstand working temperatures (up to 300°C). Furthermore, copper foils, used in the production of printed circuit boards (PCB), are passivated with chromium trioxide. The protection of the matt side is crucial to avoid any adverse chemical reactions between the treatment and the resin. Chromates support the avoidance of any lateral corrosion effects that may occur during the etching process of the conductors. Damage to these parts could significantly impair operations. Prevention of such damage is often necessary to ensure safety and even public health (e.g. in the food industry). Particular performance criteria are set to ensure safety as well as reliability. Specialist equipment manufacturers (often SMEs) rely on prevailing technology to meet these requirements: such SME cannot afford significant research and development (R&D) initiatives. Approval processes for trucks are very similar to the automotive-sector. Based on the current state of research, it will be 10 years at least before an alternative to surface treatment using chromium trioxide is available within the general engineering sector and heavy vehicle sectors.
5 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Food packaging: Articles intended for contact with foodstuffs have to meet a number of detailed requirements. When canning foodstuffs, a necessary aim of the food packaging sector is to obtain a shelf-stable product that can be stored for a considerable length of time (typically one to five years under ambient storage conditions) without suffering spoilage, while retaining desirable nutritional and sensory qualities. This requires, inter alia, that the inside of the can must be resistant to damaging effects of its contents, and the outside of the can must be resistant to corrosion under reasonable storage conditions. A crucial material used in this sector is electrolytic chromium coated steel (ECCS), a low carbon, mild steel, coated equally on both sides with a complex layer of metallic chromium and chromium hydroxides. The primary function of chromium is to provide a surface for excellent lacquer or paint adhesion. It also improves coating adhesion which is necessary for organoleptic and legislative food safety requirements. ECCS is always used with an additional coating such as a lacquer or polymer coating. ECCS is used for components that do not have to be welded, such as ends, lids, crown corks, twist-off caps and aerosol bottoms and tops. Using ECCS for packaging, the food industry is capable of processing large quantities of products in short time during harvest times and delivering these products over longer time and distance to consumers. Longer shelf life may be particularly desirable for products that have large variation in supply over years (e.g. salmon), where large strategic stocks may regulate supply to the public. To ensure performance over the entire shelf-life, testing is carried out under real-time and a range of conditions over periods of 3 and even 5 years. This requirement is a key determinant of the timescale necessary to identify an alternative anti-corrosion system for food cans. Articles intended for contact with foodstuffs must comply with EU legislative requirements for food contact. Regulation 1935/2004 aims to ensure such food contact materials neither bring about an unacceptable change in the composition or quality of the foodstuffs nor endanger the health of the consume or negatively impact on the foodstuffs’ organoleptic properties. Potential for substances present in the food contact material to contaminate the foodstuff is a foremost concern. Products that do not comply cannot be placed on the EU market. Member States may also adopt national provisions for food contact materials, such that food contact legislation is not necessarily entirely harmonised. Coatings derived from chromium trioxide surface treatment are compliant with existing regulations and generally recognised as both safe and effective. In terms of introducing alternatives to the market, the regulatory setting is critical. Where a potential alternative would involve a substance intended to come into contact with food that has not already been recognized for its absence of adverse effects in such circumstances, it may be necessary to apply for an authorisation for such substance. The food sector has guidelines, analogous to those in the aerospace sector, to manage manufacturing risk and the technology transition process, to deliver stable product technology. The assessment of a potential alternatives is ongoing. Assuming no setbacks, the industry anticipates the R&D program will require at least another 9 years. On this basis and with reference to the status of ongoing R&D, no available alternatives for chromium trioxide-based surface treatment in the food canning industry are foreseen within the next 10 years.
Identification and evaluation of potential alternatives An extensive literature survey and consultation with industry experts was carried out to identify and evaluate potential alternatives to chromium trioxide. 11 potential alternatives (including processes and substances for all parts of the process chain) are a focus for ongoing research and development
6 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
(R&D) programs and are examined in further detail in this report. Table 2 at the end of this section summarises the main findings of the AoA for the different industry sectors. The various main treatment and post-treatments processes and identified potential or candidate alternatives are discussed in chapter 7.1, while the pre-treatment processes are discussed in chapter 7.2.
Table 2: Summary of Findings of AoA (x marks technical failure, (x) marks failure not for all applications
Potential ibility Alternative (basis Maturity Sector - step process Adhesion Robustness of process &/or - term experience Food Safety Machinability Reproduc Layer thickness tension Coating
coating) One Fatigue resistance Application speed Magnetic properties Corrosion resistance Long Complex parts/geometry
Performance Failure According to Critical Criteria / Functionality Acids x x Silane/siloxane x x x Architecture Organometallics (x) (x) (x) (x) (Zr, Ti) Cr(III) (x) (x) x Acids x x x Automotive Silane/Siloxane x x Cr(III) (x) x x Gen Engineering - Passivation PVD x x copper foil Gen Engineering Other oxide x x x - GOES insulation Cr(III) x x x Organometallics x x Gen Engineering (Zr, Ti) – conversion Cr(III) (x) (x) x coatings 5-Methyl-1H- x x benzotriazol Low tin steel x x Packaging - (LTS) ECCS LTS with Silane/ x Siloxane
In summary, the analysis shows there are no technically feasible alternatives to chromium trioxide- based surface treatment systems for key applications in these sectors. Several potential alternatives are subject to ongoing R&D, but do not currently support the necessary combination of key functionalities to be considered technically feasible alternatives.
Concluding remarks A large amount of research over the last 30 years has been deployed to identify and develop viable alternatives to chromium trioxide-based surface treatment. Due to its unique functionalities and performance, it is challenging and complex to replace surface treatments based on chromium trioxide in applications that demand superior performance for corrosion and/or adhesion to deliver safety over extended periods and extreme environmental conditions. Several potential alternatives to chromium trioxide, such as Cr(III)- and organometallics-based systems, are under investigation across industry sectors. However, based on experience and with reference to the status of R&D programs, alternatives are not foreseen to be commercially available for key applications in this sector for at least 8 -10 years. A review period of 7 years was selected
7 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
because it coincides with optimistic estimates by the industry of the schedule required to industrialise alternatives to chromium trioxide. It also reflects the duration of the standard review period indicated by ECHA.
8 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
2. INTRODUCTION
2.1. Substance The following substance is subject to this analysis of alternatives:
Table 3: Substance of this analysis of alternatives.
# Substance Intrinsic property(ies)1 Latest application date² Sunset date³
Chromium trioxide Carcinogenic (category 1A) 1 EC No: 215-607-8 21.03.2016 21.09.2017 Mutagenic CAS No: 1333-82-0 (category 1B)
1 Referred to in Article 57 of Regulation (EC) No. 1907/2006 ² Date referred to in Article 58(1)(c)(ii) of Regulation (EC) No. 1907/2006 3 Date referred to in Article 58(1)(c)(i) of Regulation (EC) No. 1907/2006
This substance is categorized as substance of very high concern (SVHC) and is listed on Annex XIV. Adverse effects are discussed in the Chemical Safety Report (CSR). When brought in contact with water, chromium trioxide (EC No 215-607-8) forms two acids and several oligomers: Chromic acid (EC No 231-801-5), Dichromic acid (EC No 236-881-5), oligomers of chromic acid and dichromic acid (further referred as "Chromic acids and their oligomers"). This AoA discusses many situations where this is the case. For the purpose of this document the terms chromic acid is synonymous with a mixture containing chromium trioxide and water.
2.2. Uses of chromium trioxide Chromium VI containing substances have been widely used since the mid of 20th century. The major uses of chromium trioxide in CTAC for surface treatment for miscellaneous sectors are as follows: - Pre-treatment processes (e.g. Functional Cleaning, Pickling, Etching, Deoxidizing, Stripping of various substrates such as Aluminium, Magnesium, steel); - Passivation processes (e.g.: of various types of steel, copper foils, cadmium, aluminium, magnesium and zinc substances and coatings, alloyed or not); - Chemical conversion coating (CCC) (e.g.: CCC by dip process, brush process or pre- treatment to provide paint adhesion and corrosion protection, CCC by dip process and/or brush process –or with no paint applied afterwards); - Chromic acid anodising (CAA) including associated CrO3 processes (CAA with and without chromium trioxide sealing for corrosion protection of aluminium components; chromium trioxide sealing after chromate-free anodization); - Grain-oriented electrical steel insulation; and - Electrolytic chromium coated steel (ECCS). An overview of the respective surface treatment processes and their applications can be found in Table 4.
2.3. Purpose and benefits of chromium trioxide Chromium trioxide offers a broad range of functions, mainly based on the characteristics of the Cr(VI) compound. It has been widely used for over 50 years in the industry in various applications. The multifunctionality of chromium trioxide provides major properties to the surfaces treated with the respective process. The following key functionalities are discussed in more detail in chapter 3.3:
9 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
- Corrosion resistance: excellent corrosion protection and prevention to nearly all metals in a wide range of environments; - Active corrosion inhibition: when a coating is damaged, e.g. by a scratch exposing the base material to the environment, the solubility properties of the chromates allow diffusion to the exposed area and inhibit corrosion; - Adhesion promotion (adhesion to subsequent coatings or paint); - Providing low electrical contact resistance (resistivity); - Enhancing wear resistance; - Delivering optimal layer thickness (for the respective treatment and purpose); - Enhancing chemical resistance; - Providing biostatic properties; and - Inhibiting the growth and proliferation of biological organisms. The list of fundamental users of chromium trioxide is long and comprises, but is not limited to the following industries: automotive, aeronautics (not included here), defense, marine, energy, oil & gas, electricity, building & construction, steel and non-ferrous metal, food packaging, material science, printing, paper, and many more. All these sectors depend on chromium trioxide to meet their high requirements for products used under a broad variety of conditions. Several alternatives are being tested to substitute chromium trioxide. It is a challenge to find a substitute which meets all requirements for a product, for each use, and specific applications while also being technically and economically feasible. Many alternatives are already qualified for some applications and substrates, but none of them provide all the key properties of chromium trioxide as defined in the following sections.
10 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
3. ANALYSIS OF SUBSTANCE FUNCTION Chromium trioxide is used in various industry sectors in surface treatment as illustrated in the following sections.
3.1. Use Surface treatment is aimed to modify the surface to adapt it to specific use conditions. The main uses of chromium trioxide-based surface treatments in many industrial sectors are, providing better corrosion resistance, improved paint adhesion, low electrical contact resistance or enhanced wear resistance to surfaces. This is achieved by a process chain which combines initial pre-treatment process steps preparing the surfaces for a subsequent coating, the main process providing the protective coating itself, and post-treatment process steps. Corrosion prevention is a very challenging task. Metal surfaces can be influenced from corrosion by a broad variety of factors, including but not limited to: - Temperature; - Humidity; - Salinity of the environment; - Industrial environment; - Geometry of parts; - Surface conditions; - Erosion; - Radiation; - Impurities; - Stress; - Pressure; - Biological growth; - Accumulated liquid; - Operational fluids; and - Galvanic coupling (e.g. at fasteners adjacent to dissimilar metals). Uses for the main industrial sectors are described below. Automotive industry Chromium trioxide is used by automobile supply chains to manufacture several thousand parts per vehicle manufacturer. Parts, which depend on the use chromium trioxide, cover a wide range of applications from belt locks, bumpers, cylinder heads, wheels, gear box housings to injector valves in vehicle models. The use of chromium trioxide as the passivation agent for several substrates used has always presented numerous advantages for the automotive sector, which include high corrosion resistance, the self-healing properties of the deposit which endow it with good resistance to damage, a relatively low cost, related to the use of widely available raw materials, and finally a range of available colours including blue to iridescent yellow, olive drab and black. Depending on the application, further functionalities are required such as anti-adhesive properties, high hardness, chemical resistance, and variable thickness. The processes covered in this dossier are applied for commercial vehicles. Architectural The use of chromium trioxide is widely accepted by the aluminium-finishing industry, e.g. for the continuous coil coating of architectural aluminium. By far the largest market for coil coated steel and aluminium is the architectural market, where the building envelope represents the main use. Another
11 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
type of chromium-based coating, chromium phosphate coatings (consisting mainly of hydrated chromium phosphate, chromium(III)oxide and aluminium oxides) are used as a paint base in doors, windows and other exterior applications. Coating the surface of structural aluminium provides not only great aesthetic appearance but also guarantees anti-corrosion protection for architectural applications. Multiple regulations and technical requirements demand different types of coating depending on factors like price, specifications, aggressiveness of the environment, aesthetics, etc. Therefore, applying the correct type of coating on structural aluminium can increase its overall performance. In regard to corrosion protection, it is necessary to coat the metallic surface with a passivation layer which delivers high anti-corrosive properties and increased adhesion for the subsequent coating layers. Layers derived from chromium trioxide use can achieve both, and this is the reason why this kind of coating has been successfully applied for many years. For example, yellow chromate is mostly used in coatings for structural and architectural applications.
Packaging industry Steels for packaging are usually low carbon steels, tin or chromium coated on both sides. This combination of characteristics gives high performance properties, for example strength and stiffness, welding ability, good lacquerer adhesion, aesthetic appearance and corrosion resistance, which provides content protection during stocking and transport, safe food and beverage preservation, and other relevant functionalities. In this context, a multilayer coating of the steel guarantees the required performance for each different food packaging application. Passivating chromium and chromium oxide layers are therefore applied onto the metallic substrate usually by means of an electrolytic chromium coating in a bath using chromium trioxide, which deposits elementary chromium (Cr(0)) and Cr2O3 on the plate. Packaging steels with chromium trioxide coatings find diverse applications in the food packaging industry, for example in food and beverages cans, twist-off caps for jams, etc. In addition to the critical parameters mentioned above, each packaging application has its specific performance requirements, for example regarding shelf life, pack and cycle performance. General engineering The steel processing industry utilises several surface treatment applications requiring chromium trioxide. Engineering coatings are produced to enhance the properties of the substrate. It is often combined with functional surface coating which enables a product to fulfil its function more effectively. Chromium trioxide conversion coating is applied on various substrates and coatings to enhance corrosion resistance and paint adhesion. Optical properties also play a crucial role as customers in the current highly competitive market are very sensitive to aesthetic aspects. Colour coating /coil coating is a continuous process for providing paint or film coating to strip metals, primarily steel and aluminium. Up to three separate coating layers are applied onto one or both sides of the metal strip surface. The relevant process steps with regard to the use of chromium trioxide are cleaning and pre-treatment. A Cr(VI) passivation layer is applied after a series of pre-treatments to increase corrosion resistance and to improve adherence of subsequently applied coatings. The range of applications for coil coated metals is vast. Coil coated metals are used wherever the end use demands a high-quality painted finish on a component fabricated from sheet metal. In the transport sector, coil coated materials are used in parts such as trailer bodies and recreational vehicles, but also in a variety of components such as oil filter caps and wiper blade assemblies. Coil coated metal is used as a pre-primed surface for the body-in-white of cars, providing a high-quality base for application of customised automotive paint coatings.
12 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Chromium trioxide is used as a component of the final coating on grain oriented electrical steels (GOES). These steels are produced mainly for electrical transformers (power and distribution transformers) for which they offer vital properties. Chromium trioxide is applied in the insulation layer which has to be resistant to corrosion and chemicals such as transformer oils and to withstand working temperatures (up to 300°C). In addition, lower noise levels and smaller core sizes in transformers can be achieved with the use of chromium trioxide. With regard to energy efficiency and the increasing production of electric cars, the importance of grain-oriented steel is expected to further increase in the future. Furthermore, copper foils used in the production of printed circuit boards (PCB), are passivated with chromium trioxide. The protection of the matt side is crucial to avoid any adverse chemical reactions between the treatment and the resin. The use of chromium trioxide supports the avoidance of any lateral corrosion effects that may occur during the etching process of the conductors. Furthermore, they keep a high bond strength on thin conductors, as the integrity of the interface between the matt side and the resin remains unaffected. Copper foils are treated through several processes to improve their reliability and processability: heat resistance, no oxidation and compatibility with different substrates is necessary, since the passivated cooper foil has to be laminated with various resins. In 2012, the turnover of the European coil coating industry was estimated to be € 5.5 billion with an output of 1240 million m2 of coated metal. (ECCA, 2012).
3.2. Surface treatment processes Surface treatment of metals is a complex step by step process in many industry sectors. For operations with high performance surfaces in demanding environments, the use of chromium trioxide is essential to ensure the long-term quality (over decades) and safety of the endproduct. As specifically illustrated in Figure 2, there are various steps within the whole surface treatment process. These are classified into pre-treatment processes (for an adequate preparation of the substrate for subsequently applied process steps), treatment processes (main process), and post-treatment processes (which mostly have to be applied for final surface protection). Some examples are listed in Table 4, but the table is not exhaustive.
Use Description Surface Treatment of Metal Parts
Pre-Treatment Treatment Post Treatment • Cleaning • Conversion Coating • Sealing after Anodizing • Pickling/Etching • Anodizing • Passivation • Deoxidising
Figure 2: Surface treatment processes steps where chromium trioxide might be involved
Only the combination of adequate pre-treatments, main process step and post-treatment leads to a well-prepared surface providing all necessary key requirements for the respective applications (as described in detail in chapter 3.3.2. To be clear, the use of chromium trioxide in at least one process step is crucial to ensure the quality of the product and to meet the requirements of the industry.
13 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Although single process steps can be assessed individually, they cannot be seen as stand-alone processes but as part of a whole process chain. Consequently, when assessing alternatives for chromium trioxide-based surface treatments, the whole process chain and the performance of the end product has to be taken into account. While R&D on replacement technologies in surface treatments has been ongoing for decades, industry has developed and has already partly qualified alternate treatments for special applications. However, it is crucial to consider the following points: - In each case, the performance of the alternative materials/techniques must - importantly - be evaluated as part of a whole system (Figure 2), - Any change of single steps in the process chain of surface treatments will require component and/or system level testing and evaluation, (re)qualification and implementation into the supply chain; and - Most approvals for coating systems still incorporate at least one layer prepared with chromium trioxide. We therefore clearly state that for a thorough assessment of replacement technologies, it is mandatory to include the whole process chain (including pre- and post-treatments), taking into consideration that for all steps involved, Cr(VI)-free solutions have to be developed, which in combination are technically equivalent to the current Cr(VI) containing treatments. Currently, no complete chromium trioxide-free process chain is industrially available though for key applications providing all the required properties to the surfaces for all applications.
Table 4: Overview of surface treatment processes indicating most important application methods, purpose, as well as example products. This is not intended to be an exhaustive list.
Process Application Purpose Product/Substrate examples
Cleaning of copper and copper Bath Surface preparation for subsequent - Functional alloys, magnesium and Wipe processing. cleaning magnesium alloys Spray Removing surface contamination - Electropolishing of steel Removal of mechanically deformed layers, oxides or other compounds from a metal surface by chemical or - Pickling of stainless steel,
Pickling/ Bath electrochemical action. molybdenum Etching Spray Removal of material selectively to - Pre-treatment of Al alloys, Cu reveal a surface or the surface properties.
Deoxidising is a pre-treatment step Pre-treatment of Al alloys prior Deoxidising Bath required to activate the surface prior to - to anodising
treatment processes further processing. -
Pre - Pre-treatment of metallic Removal of metal sulphide and other substrates (stainless steel, Desmutting Bath complexes after etching molybdenum) after pickling, etching and deoxidising Stripping of organic and Bath Stripping is the removal of a coating - inorganic material, such as paint Stripping Wipe from the component substrate or an from steel or hard anodic undercoat. Brush coating from Al alloy, Mg alloy
Aluminium Bath - Chemical Chemical process that introduces a Magnesium conversion Spray chemical coating or changes the - Steel coating Wipe surface of the substrate to improve the - Conversion coating of metallic (CCC) Brush substrate properties (e.g. corrosion - Main process coatings
14 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Process Application Purpose Product/Substrate examples Coil resistance, or promote adhesion of coating subsequent coatings) Electrolytic oxidation process in which - Bumpers, cylinder heads, wheels, gear box housings Chromic acid Bath the surface of a metal, when anodic, is anodising converted to an oxide having desirable - Building components (CAA) Brush protective or other functional - Small parts: fasteners, connector properties. shells Chromium coated steel is a sheet or Electrolytic strip of steel electrolytically coated chromium Crown corks, twist-off caps and Bath with a layer of chrome thinner than a - coated steel aerosol bottoms and tops micron. It is also known as TFS (Tin (ECCS) Free Steel). Grain A coating that is applied to steel strip Power transformers, shunt oriented steel Bath or steel sheet for the manufacture of - reactors, power generators insulation electrical apparatus.
Sealing after Bath Sealing of the porous anodic coating - Anodised aluminium surfaces
anodising Brush providing protective properties for corrosion resistance Passivation of Chemical process applied to a
treatment copper foils - substrate producing a superficial layer - Production of printed circuit processes (Post- Bath containing a compound of the substrate boards (PCBs) Post treatment metal and an anion of an environment. CCC)
3.2.1. Pre-treatment processes A number of pre-treatments are necessary to prepare the surface of the substrates for the subsequent process steps. Adequate preparation of the base metal is a prerequisite: adhesion between a coating and the substrate depends on the force of attraction at molecular levels. Therefore, the surface of the metal must be absolutely free of contaminants, corrosion and other foreign matter until the main treatment process is finished. Additionally, homogeneous formation of anodic films or passivation is influenced by the pre-treatment. Inhomogeneous surfaces will result in unpredictable corrosion performance. A number of different pre-treatments are in place depending on the respective subsequent process and its functionality. The pre-treatments discussed below are based on the use of chromium trioxide, while chromate-free pre-treatments are discussed in chapter 7 (evaluation of alternatives).
3.2.1.1 Functional cleaning All surfaces have to be prepared for subsequent processing by removing dirt, soil, scale and oxide layers. Chromium trioxide functional cleaning solutions are used for achieving best results. Functional cleaning is not a stand-alone process but part of a process chain. Presence of those contaminants influences the appearance of the subsequent layer and increases the susceptibility for fatigue and pit corrosion. For electropolishing, chromium trioxide is used for buffering and assisting in rinsing off the solution after completing the process. The process is used to remove flaws or debris from the surface of a metal substrate. Electropolishing can also be described as a “reverse plating” process as it is carried out in a blended chemical electrolyte bath using a combination of rectified current. For electropolishing of martensitic stainless steel, the use of chromium trioxide mandatory. It improves
15 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
the fatigue behaviour of structural parts and effectively eliminates impurities from previous thermal treatments. Control of pH can only be done by chromium trioxide.
3.2.1.2 Pickling and etching There is considerable overlap between these terms in the industry. Pickling/Etching is the removal of mechanically deformed layers, oxides or other compounds from a metal surface by chemical or electrochemical action. Etching is also used to remove smear in order to ensure the detection by dye penetrant inspection of cracks or other defects formed during metal shaping such as machining or forming. Typically it removes 0.5 to 3 µm of the substrate, and it is required because the initially unprotected metal surfaces exposed to atmospheric conditions are continuously oxidised. These oxides interfere with subsequent processes (e.g. in passivation the required optimal corrosion protection could not be reached). With regard to aluminium alloys, pickling/etching is additionally used to enhance the surface for adhesive bonding for subsequent processing. Pickling/etching is not a stand-alone process but part of a process chain. Chromium trioxide is used as it is a strong oxidising agent offering the strongest reduction behaviour and therefore also the best result for tailoring of surfaces. In addition, the use of chromium trioxide-based pickling/etching solutions has a very low impact on the fatigue properties of the treated substrate. Strongly alkaline solutions containing chromates may also be used for specific metals. Specialized applications are when processing steel before bonding or photochemical machining (PCM) of stainless steel or molybdenum. This chromium trioxide-based surface treatment is used for the removal of contamination from the surface prior to bonding to create a clean surface and to ensure adequate adhesion of the subsequent bonded layer. The process consists of several steps, the main one being an electrolytic process and a subsequent desmutting step which uses chromate loaded products. The process removes material/contaminations from the surface and creates a surface topography beneficial for subsequent bonding. The process enables stainless steel to be bonded to other materials independent of type or to adequately prepare and/or desmut stainless steel or molybdenum within the PCM process.
3.2.1.3 Deoxidising Deoxidising is a pre-treatment step required to activate the surface prior to further processing. Deoxidising is not a stand-alone process but part of a process chain. Deoxidising is an intermediate process step after degreasing and cleaning prior to subsequent process steps, such as anodizing or conversion coatings. Chromium trioxide-based deoxidising is able to fulfil a number of different purposes, depending on the initial pre-treatment and the required subsequent process. As an example, both the pre-treatment processes degreasing and etching are performed under alkaline conditions while a subsequent anodizing is performed under acidic conditions. Therefore, the surface has to be neutralized after the pre-treatments prior to the anodizing process. As a further purpose, deoxidising also removes potentially remaining oxides from the metal surface and activates the surface for the subsequent processes. The chromium trioxide-based deoxidiser solutions often comprise additives such as nitric acid (HNO3) and hydrofluoric acid (HF), depending on the specific purpose. According to Harvey et al. (2008), these deoxidisers remove around 1 µm of the surface during the treatment, including the surface oxide and the majority of the intermetallic particles leaving the surface with a chromium containing oxide.
16 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Mode of action for Aluminium pre-treatment by cleaning, pickling/ etching/ deoxidising: The general mode of action for cleaning, pickling, etching and deoxidising is basically the same. The purpose of all these steps is the removal of oxides and of certain amounts of the base metal from the surface. There are numerous chemical reactions involved with the different constituents of the deoxidising solution, the aluminium oxide layer on the part surface, and the alloying elements (e.g. Cu, Si, Mg, Zn) of the substrate. While many of the reactions are intended there are also many unintended reactions. The role of chromates in the deoxidiser solution is primarily to provide uniform removal of aluminium and alloy metals and activate the surface for subsequent processing.
3.2.1.4 Stripping Stripping is the removal of a coating from the component substrate or an undercoat. Chromium trioxide-based stripping solutions can be used for a wide range of substrates and coatings, while it turned out when considering alternatives, the stripping process always has to be adapted taking into account the substrate (metal, specific alloy type) and the kind of coating to be removed. Therefore, stripping can be divided into two main processes as there are, (i) stripping of inorganic finishes (such as hard anodic coating from Al alloys), and (ii) stripping of organic finishes such as primer and/or paint (from steel, aluminium, nickel/cobalt alloys, titanium, magnesium, corrosion resistant stainless steel CRES). Stripping is used to remove the coating (for example an anodic coating applied by CAA) without attacking the aluminium substrate itself. This process is used for rework, maintenance and repair operations, when the coating has to be removed and repaired, for example as partial repair. Stripping of coatings which had been applied more than 10 years ago requires higher temperatures, while “younger” coatings are more easily removed. Stripping is not a stand-alone process but part of a metal pre-treatment process chain.
3.2.2. Main surface treatment processes In the following chapter, various main treatment processes that are applied on surfaces within different industry sectors are described.
3.2.2.1 Chemical conversion coating (including phosphate conversion coating: phosphating) CCC is a chemical or electrolytic process applied to a substrate producing a superficial layer containing a compound of the substrate metal and the process chemistry. In general, CCC form an adherent, fixed, insoluble, inorganic crystalline or amorphous surface film of complexes from oxides and chromates or phosphates as an integral part of the metal surface by means of a chemical reaction between the metal surface and the immersion solution. CCC is usually carried out by immersion of the product in an acidic bath with an aqueous solution containing dissolved chromate or phosphate salts together with an acid such as sulphuric acid or nitric acid. CCC can also be applied by spray or wipe techniques, more common in repair and non-stationary operations. The thickness of the coating typically is between 0.05 – 2 µm. There are two main classes of products which are subject to a CCC treatment, the first are products made of aluminium and its alloys (Al CCC) and magnesium and its alloys (Mg CCC). The second are metallic coatings such as aluminium-based coatings, zinc-based coatings, zinc-nickel-coatings and cadmium coatings applied on metallic substrates (such as steels, stainless steels, aluminium, copper etc…) where CCC is used to provide corrosion protection. This process is further referred to
17 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
and discussed as passivation of metallic coatings. Indeed, other metals can also be subject to conversion coatings. CCC are used throughout the industry on a wide variety of components and equipment such as steel landing gear components, fasteners, electrical connectors and enclosures. Mode of action: Various research efforts have been made leading to considerable understanding of the mechanism of metal corrosion and the inhibition provided by chromates as conversion coatings over the last decades. The formation of a CCC includes several steps, typically starting with a deoxidising and degreasing pre-treatment to prepare the substrate’s surface, followed by the main process step of dipping the substrate in the chromate solution (Vasques et al, 2002). The chemical reactions provided below are specific to aluminium substrate; however, the general mode of action for magnesium substrate or metal coatings are basically the same. According to Vasques et al (2002) and Zhao et al (2001), aluminium exposed to a chromate conversion coating solution results in the simultaneous oxidation of Al to Al3+ and the reduction of Cr(VI) to Cr(III) as follows: (1) 2 Al 2 Al3+ + 6e–
3+ + (2) 2 Al + 3 H2O Al2O3 + 6 H
2- + - (3) 2 (CrO4) + 10 H +6e 2 Cr(OH)3 + 2 H2O. The result is a protective layer based on chromate anions, absorbed in the pores of the aluminium oxide layer. As residual chromium trioxide is retained in the CCC, it provides active corrosion inhibition to the surface by diffusion into local defects and altering the local environment. Any comparison of an alternative for chromium trioxide in CCC must take this unique property into consideration (Zhao et al, 2001). According to Zhao et al (2001), the mechanisms for the inhibition of metal alloy dissolution 2- 2- are that the chromate is a very soluble, higher-valent, oxidising ion (CrO4 or Cr2O7 ) with a lower valent form that is insoluble and creates an extremely protective film (Cr(OH)3). The degree of corrosion resistance of conversion coatings is generally proportional to the coating thickness (Deresh, L., 1991).
3.2.2.2 Chromic acid anodising (CAA) CAA is an electrolytic oxidation process in which the surface of a metal, when anodic, is converted to a coating having desirable protective or other functional properties. The oxide layer partly grows into the substrate and partly grows onto the surface. The total oxide thickness after anodising is between 3 and 60 µm, while the thickness after hard anodising is up to 300 µm (Feßmann and Orth, 2002). CAA comprises a number of different process steps including pre-treatment and post-treatments. Anodising is used to increase corrosion and wear resistance as well as adhesion for subsequent processes. Substrates that can be treated by anodising include aluminium alloys, titanium, magnesium, niobium, zirconium, hafnium and tantalum. The main commercial application is the treatment of aluminium to create alumina (Al2O3) on the surface (RPA Report, 2005). CAA is performed in an acidic solution containing chromium trioxide and in some cases other acids. The parts to be treated form the anode electrode of an electrical circuit, the respective cathode is inert. The electric current can be varied which leads to oxidation of the base metal at the anode with the formation of aluminium oxides on the surface. Some of the aluminium is dissolved, as ions, into the process bath which leads to bath losses and the need to replace some of the bath solution.
18 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Anodised aluminium surfaces, for example, are harder than aluminium but have low to moderate wear resistance that can be improved with increasing thickness and still have low corrosion resistance that can be improved by applying suitable sealing substances. Anodic films are generally much stronger and more adherent than most types of paint and metal plating, but also more brittle. This makes them less likely to crack and peel from aging and wear, but more susceptible to cracking from thermal stress. The unsealed anodised surfaces provide a good paint adhesion to subsequent layers, but need to be sealed or primed for providing a good corrosion protection (Fast Report, 2009). The thickness of a CAA surface is typically in a range between 0.5 to 18 µm. This is significantly thicker than the natural oxide surface of an untreated aluminium surface (which is typically 0.005 µm) and thinner than surfaces created by non-chromate Sulphuric Acid Anodising (SAA) (which is typically 15 µm and greater).
Figure 3: Schematic anodic coating after acidic anodising (Hao & Cheng, 2002)
Mode of action: CAA improves the corrosion resistance of aluminium or aluminium alloy surfaces by anodic treatment in an electrolytic bath by forming aluminium oxide (Al2O3). The oxidisation and reduction process is analogous to CCC but the anodic film formation is mainly driven by the applied voltage during the anodizing cycle (refer to equations 1 to 3 above).
3.2.2.3 Electrolytic chromium coated steel (ECCS) / tin-free steel (TFS) Electrolytic chromium coated steel is also known as tin-free steel (TFS): a low carbon, mild steel, coated equally on both sides with a complex layer of metallic chromium and chromium hydroxides. The chromium plating of the steel strip is performed electrolytically in a chromium trioxide bath. The steel strip is passed through the entry section of the line, cleaned, pickled, treated electrolytically in a solution derived from chromium trioxide, rinsed thoroughly, dried, oiled, and then recoiled.
Figure 4: TFS composition illustrated with a schematic cross section. (www.jfe-steel.co.jp)
The primary function of chromium trioxide is to provide a surface for excellent lacquer or paint adhesion. It also improves coating adhesion which is necessary for organoleptic and legislative food safety requirements. ECCS is always used with an additional coating such as a lacquer or polymer coating. Polymer-coatings (PET or PP) are applied either by laminating film or extruding polymer
19 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
directly onto the substrate, usually on both sides. Furthermore, it is very resistant to heat, to alkali milieus and to black sulfide stain. The latter function makes it the most suitable material for fish cans. ECCS is used for components that do not have to be welded, such as ends, lids, crown corks, twist- off caps and aerosol bottoms and tops. The chromium plating step is generally preceded by a pre-dip, in order to prepare the surface of the strip for electrodeposition and to prevent stains and other surface defects forming on the surface of the strip (sulphuric acid solution). The strip is then passed through an electrolyte containing Cr(VI) ions, which are reduced cathodically on the strip surface to form a duplex layer of hydrated chromium oxide and metallic chromium. A typical plating electrolyte consists of chromium trioxide (110 - 130 g/l) and hydrofluoroboric acid (0.30 - 0.44 g/l) and sulphuric acid (0.60 - 0.80 g/l), the latter two acting as catalysts to improve the efficiency of the plating process.
Figure 5: Tin plate cross section (www.jfe-steel.co.jp)
3.2.2.4 Grain-oriented electrical steel (GOES) insulation GOES is used for the manufacture of magnetic cores within transformers. Low power loss and high permeability characteristics are advantegous where energy efficiency, low noise and core size are important (e.g. power generators, large power transformers, distribution transformers, small transformers, shunt reactors, wound cores). The higher the frequency of the application, the thinner the thicknesses of the steel sheets should be to reduce negative effects of core losses due to eddy currents and reduce heat build-up.
Figure 6: Illustration of non-oriented and grain-oriented electrical steel (http://www.thyssenkrupp.com)
20 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Optimum magnetic properties are attained for the rolling direction, due to the nature of the manufacturing process. If the material is magnetised off the rolling direction, the core losses increase significantly. The extent of this increase varies from a factor of three at 90 degrees and four at 60 degrees. It is therefore essential that the material is magnetised as precisely as possible along the rolling direction throughout the magnetic circuit. Generally, chromium trioxide is used for GOES to cover both sides with a thin inorganic coating. The coating is approximately 2-5 µm thick per side and provides good electrical resistance (insulation up to >10 Ω/cm2) with marginal effects on the stacking factor. It has good adherence properties, and will withstand normal punching operations. Furthermore, it is resistant to annealing up to 840 °C in non- oxidizing atmospheres. The coating is chemically resistant to any fluid contamination during the production process, provides corrosion protection, is unaffected by different types of transformer oils, and introduces tension into the strip (improving the magnetic quality of GOES). The coating tension is a key requirement, provided by chromium trioxide, for this application. The American Society for Testing Materials (ASTM) A976-13 classifies insulating coatings for electrical steels by composition, relative insulating ability and application.
3.2.2.5 Passivation of copper foils Copper foils are used in the production of printed circuit boards (PCBs). Conversion coatings with chromium trioxide are used to protect copper foils from corrosion and tarnishing under harsh conditions. These conversion coatings are created using electrolytic reduction on the cathodic non- ferrous surface. Copper foils are treated through several processes to improve their reliability and processability. There are two types of copper foils: rolled copper and electro-deposited copper. Rolled copper foil is recommended for thermal shock environments and for applications with high frequencies in the flexible PCB industry and high-frequency PCB industry. Electro-deposited copper has a vertical grain structure which is advantageous for obtaining tight-etched spacing and well defined conductor walls.
Figure 7: Rolled copper foil treatment process. (Lu D., Wong CP., Materials for Advanced Packaging, 2009, p.290, Fig. 8.11)
Both types of copper foils have a rather low surface roughness on the top side (shiny side) between 0.3 and 0.5 µm. The dielectric bottom side (matt side) is pre-treated to obtain the desired surface topography through either mechanical roughening, or chemical roughening or levelling. The matt side is pressed together with a resin impregnated glass cloth and thus forms a copper clad laminate (laminate). These laminates are the base material for the fabrication of PCBs, widely used for electronic, automotive and industrial equipment. Surface roughness is important to promote adhesion to dielectric materials or to create photo resists during PCB fabrication. Excessive surface roughness can be detrimental to both electrical conductor
21 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
losses at high signal frequencies and to controlling the print-etch process when forming fine PCB features. The surface roughness of the bottom dielectric side of rolled copper foils is lower (approx. 0.5 µm) than for electrodeposited copper foils (between 0.5 µm - 4 µm). High surface roughness can increase conductor loss of a microwave circuit as frequency increases.
Figure 8: Electrodeposited copper manufacturing process (Rogers Corporation, Copper Foils for High Frequency Circuit Materials, 2014) Sufficient foil adhesion is a prerequisite. The adhesion of resin systems to metals is a mechanical process. Therefore, the bond strength is directly related to the surface roughness of the treated foil side. Because the surface roughness of rolled copper is not sufficiently adhesive, additional surface treatment is required in order to create reliable chemically bonded assemblies. The protection of the matt side is crucial to avoid any adverse chemical reactions between the treatment and the resin. Chromates support the avoidance of any lateral corrosion effects that may occur during the etching process of the conductors. Furthermore, they keep a high bond strength on thin conductors, as the integrity of the interface between the matt side and the resin remains unaffected. The shiny side of the laminate must also be protected to prevent oxidation or tarnishing, which may adversely affect the subsequent process steps (e.g. photochemical processes, etching of PCB structures). The conversion coatings are very thin, generally below 15 nm. Thus, the amount of Cr(VI) present on these copper foils is extremely low with approx. 0.02 to 0.03 mg/m².
3.2.3. Post-treatment processes A number of different, chromium trioxide-based post-treatment processes can be applied to the surfaces as described below.
3.2.3.1 Sealing after anodizing The surfaces of substrates after anodizing are naturally porous, the coating cannot provide the required corrosion resistance without further treatment (Hao & Cheng, 2000), therefore a sealing post-treatment is necessary for a broad variety of sectors and applications. Sealing is often performed in a hot aqueous chromate solution (typically > 95°C but below the solution’s boiling point) using either sodium dichromate, potassium dichromate or a mixture. For
22 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES some applications, hot water or salts of other metals are used for sealing. Chromium trioxide- conversion coating solutions can also be used for the purpose of sealing after anodizing. Mode of action: The sealing after anodizing step is performed with a dichromate solution comprising chromium trioxide, sodium dichromate, potassium dichromate, or a mixture thereof. During the sealing, chromates and hydroxides precipitate in the pores of the previously anodized oxide layer and are hydrated. By this process, the pores are closed and an adequate wear resistance and corrosion resistance is provided to the surface. The hydration process (in the course of sealing after anodizing) is pH dependent, but in all cases, the chromate is absorbed to the anodized aluminium surface. Depending on the pH, Cr(VI)-based sealing forms either aluminium oxychromate (equation 1) (at pH lower than 6) or aluminium dioxychromate (equation 2) in the coating micropores (Steele & Brandewie, 2007).
- - (1) AlOOH + HCrO4 AlOHCrO4 + OH - - (2) (AlO(OH))2 + HCrO4 (AlO)2CrO4 +OH +H2O The final step closes the pores by contact with hot water and locks in the chromium trioxide in the pores according to equation (3):
(3) Al2O3 + H2O 2 AlO(OH). The hydrated aluminium oxide (boehmite) has a larger volume than aluminium oxide, therefore the pores are closed.
3.3. Key chromium trioxide functionalities in surface treatment processes An overview on the key functionalities and the performance requirements of chromium trioxide in the respective surface treatment is provided in the paragraphs below, subdivided into pre-treatment processes, main processes and post-treatment processes. During the consultation phase, the key functionalities for chromium trioxide within this use were identified taking the whole surface treatment processes into account. Nevertheless, the most important key functionality for all the main processes and post-treatment processes is corrosion resistance. It should be noted that while the numerical values reported for key requirements here have been supplied by industry, they are not necessarily the same for all companies. Furthermore, requirements for individual applications may also vary.
3.3.1. Pre-treatments - key functionalities As stated in chapter 3.2.1., a clear demarcation between the processes of pickling, etching, cleaning, and deoxidizing does not exist. When comparing specifications from different sources, the terminology is not always consistent from one document to another. It can be stated that with all these processes, adequate surface preparation for subsequent steps can be achieved by removal of surface residues. The main difference is that for cleaning, a less aggressive chemistry is used for light scale removal or removal of other contaminants like shot peen residue. As the aim of the pre-treatment processes is to prepare the surfaces for subsequent process steps, the key functionalities are not always the same as for the main process or the post-treatments discussed in chapter 7.1.
23 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
3.3.1.1 Functional cleaning, pickling, etching The key functionality of cleaning, pickling and etching is the adequate removal of oxide and debris from a metal surface (e.g. aluminium, magnesium, cadmium). For pickling and etching, selective removal of certain amounts of base material or removal of surface defects is required for surface activation. This process is controlled by the etch rate. The careful control of this step influences the quality of the subsequent coating layer. After these pre-treatments, the processed parts shall be free of pits, corrosion products, discolouration, uneven etching, increased surface roughness or other defects that would prohibit further chemical processing. This can be checked by visual inspection or penetrant inspection (ASTM E 1417). The etching rate has to be adequately chosen depending on the metal substrate. Under-etching or over-etching has to be avoided so that the key functionalities of the subsequent layer are not affected (for example: poor adhesion resulting in cracks and blistering). The etch rate is typically controlled by measuring the weight before and after on a witness coupon at a regular interval. In addition, treated surfaces shall be free of intergranular attack in a defined excess or end grain pitting in distinct limits. Further it is important that the baths can be used for a long timeframe with manageable maintenance. Additionally, the racks carrying the parts are usually used in the overall process chain and therefore have to be compatible with the chemicals used in the subsequent process steps.
3.3.1.2 Deoxidising With a chromium trioxide-based deoxidising process step, the key quality criteria is to provide surface activation. The deoxidising causes a metal removal of the substrate, which shall not exceed certain limits (physical measurement using a micrometre). By applying a deoxidising solution, the metal is attacked and end grain pitting and intergranular attack may be caused. Deoxidising shall neither cause end grain pitting nor intergranular attack in certain excess and depth. Furthermore, the appearance of the deoxidised surface (after rinsing) is visually inspected. It has to be a water break free surface without streaks or discolourations and no pitting or selective attack to the substrate, no non-rinseable residuals, or contamination from the deoxidising solutions shall be observed on the surface.
3.3.1.3 Stripping of inorganic finishes Specifications require no hydrogen embrittlement during 200 h of sustained load according to ASTM F 519, although the effect of the hydrogen can be removed to a certain extent by subsequent de- embrittlement heat treatment. End grain pitting and intergranular attack negatively influencing the substrate quality, shall not exceed a ratio of (surface) pit size to pit depth of 6:1, which is tested according to ASTM F 2111. Stripping of the inorganic coating may have an impact to a shot peen compressive layer, which can affect the fatigue properties. However, no more than 10% of the thickness of the shot peen layer shall be removed, which is tested by a micrometre. As a certain amount of the base material may be removed by stripping, it must be guaranteed that the parts still conform to the drawing after stripping. This is tested by post processing inspection measurements. Stripping of an inorganic finish from Ti alloys may leave a notable hydrogen content on the substrate, which is tested according to ASTM E 1447. The hydrogen content can cause hydrides to precipitate, which then can lead to embrittlement and cracking under stress. Other parameters which may affect the substrate are residual stress, surface roughness and fatigue. However, as the reason for performing the stripping process is the need to repair a coating, these parameters cannot be worse than for the original (defect) coating. Stress corrosion cracking of the
24 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES substrate is tested by exposing test specimens for 4.0 ±0.5 h in a molten salt bath. The specimens are rejected if the material shows pitting, cracking or rough etching. Chromium trioxide-based stripping solutions can be used for a wide range of substrates and coatings, while it turned out when considering alternatives, the stripping process always has to be adapted taking into account the substrate (metal, specific alloy type) and the kind of coating to be removed.
3.3.1.4 Chemical stripping of organic coatings (e.g. primers, topcoats and specialty coatings) Chromium trioxide is used as active ingredient for stripping, although the most common active ingredients in solvent brush on paint strippers include methylene chloride (dichloromethane), benzyl alcohol, formic acid or hydrogen peroxide. Different active ingredients are useful for different paint systems. Chromium trioxide used in lower concentrations would still possibly contribute to paint removal, but other active ingredients would provide most of the paint removal action. The important role of chromium trioxide is to mitigate pitting and galvanic corrosion during the stripping process. For the corrosion resistance of substrates where paint became stripped, various tests are carried out described as follows. Sandwich corrosion is tested according to ASTM F 1110. Immersion corrosion is tested according to ASTM F 483. The fluid should neither cause corrosion nor a weight change of any test panel, specific for the respective kind of substrate. Dissimilar metals corrosion is tested by immersing coupled dissimilar metal components together. The test is failed if the panels exhibit pitting, etching or corrosion products. Adhesion is tested according to International Organization for Standardization, ISO 2409, mesh peel test, long beam test and other tests depending on the process specific requirements. When stripping off paint from metal substrates, hydrogen embrittlement may occur. No hydrogen embrittlement should be observed during 200 h of sustained load according to ASTM F 519. No cracks are allowed to occur on the surface after stripping of paint. The fatigue properties are tested according to ASTM E 466 (5 stripping cycles) and no degradation should occur. For composite materials, no evidence of wet media penetration shall be detected after thermographic inspection. The surface roughness of the stripped surface is tested with a profilometer.
3.3.2. Key functionalities of chromium trioxide-based main processes & post-treatments As already stated, the described main processes and post-treatments rely on the use of chromium trioxide due to a number of key functionalities, which are described in detail below. Corrosion resistance / active corrosion inhibition Corrosion describes the process of oxidation of a metallic material due to chemical reactions with its surroundings, such as humidity, but also corrosive electrolytes. In this context, the parameter corrosion resistance means the ability of a metal aircraft part to withstand gradual destruction by chemical reaction with its environment. This parameter is one of the most important since meeting its minimum requirements plays a key role in assuring the longest possible life cycle for all the implicit parts. For zinc-coated steel, chromium trioxide protects the Zn layer from further oxidation by acting as temporary corrosion inhibitor to avoid white rust, before natural weathering takes place. The corrosion resistance requirements vary within the industry sectors and are dependent on the metal substrate (aluminium alloy, steel type), the coating thickness and the respective surface treatment process. Corrosion inhibiting components can be categorized according to basic quality criteria which are inhibitive efficiency, versatility and toxicity. Ideally, the component is applicable in all surface treatment processes, compatible with subsequent layers, and performs effectively on all major metal
25 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
substrates. Furthermore it has to guarantee product stability (chemically and thermally) and has to reinforce the useful coating properties. The ability of a material to spontaneously repair small amounts of chemical or mechanical damage is known as an active corrosion inhibition or self-healing property. If this characteristic is given for a certain material, it is tremendously advantageous and will enhance service life duration of parts and maintenance intervals. The requirements for active corrosion inhibition are varying within the industry and are depending on the metal substrate and the respective surface treatment process. The active corrosion inhibition of a chromium trioxide-based surface treatment is generally tested in line with the corrosion resistance based on the same test methods and requirements, as the active corrosion inhibition of a coating is a characteristic feature. Adhesion promotion (adhesion to subsequent coatings or paint) Depending on the final functions of the parts, they may be coated with decorative or protective layers (such as paint). In this analysis, the parameter adhesion describes the tendency of dissimilar particles or surfaces to cling to one another. Many parts are exposed to harsh environmental conditions, in contact with other metallic parts or have to withstand strong mechanical forces. The requirements for adhesion vary within the industry and depend on the specific coating thickness and the function and location of the part. Chemical resistance This parameter is defined as the ability of solid materials to resist damage by chemical exposure. It is highly important that all parts withstand contact with different chemicals like greases, oils and lubricants. The chemical modification of protective coatings or the metal parts themselves could escalate maintenance costs. The requirements for chemical resistance are varying within the industry and are depending on the metal substrate, the coating thickness and the respective surface treatment process. A general high- end chemical resistance provided by the chromium trioxide-based surface treatment is typically tested in line with the corrosion resistance based on the same test methods and requirements. More specific tests on chemicals are performed in addition. Layer thickness The thickness of the layers or coatings on the substrate are also crucial for the performance of the parts. Not meeting the specified requirements of this parameter could lead to deficiencies for other related characteristics like corrosion and chemical resistance, improper adhesion of coatings to the substrate or increased fatigue properties. Resistivity Electrical resistivity is a property that quantifies how a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Many applications require electrically conducting materials for static discharge, electromagnetic interference (EMI) shielding, and electrical bonding (e.g. lightning strike protection). A material that provides good electrical bonding between all joints is required to assist in controlling and shielding against electrical effects. Eddy current test is used to detect surface & subsurface defects, corrosion in aircraft structures, fastener holes and bolt holes. Surface defects and Resistivity testing are performed by high frequency; for detection of sub-surface defects, low frequency method is carried out.
26 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
3.3.3. Sector specific key functionalities
3.3.3.1 Architectural sector Table 5 presents a short overview of selected quantifiable requirements of the key functionalities for the main process steps and post-treatments. The selection was made regarding the most relevant process-related key functionality. A more detailed description is given in the subsequent paragraphs.
Table 5: Key requirements within the architectural sector
Process Quantifiable key functionality Requirements Depending on substrate and pre-treatment. Aluminium: 1000 h (ISO 9227) 1000 h (EN 3665), GSB F factor < 0,4 48 h, creep <0.5 mm (accelerated corrosion Machu test) Corrosion resistance Zn-coated materials: 1000 h (ISO 9227) 1000 h (EN 3665), 300 h Zn-coated steel Non-coated Zn: 48-96 h (ISO 9227) Chromium Long-term performance: >1-10 years sea- trioxide / side testing (Natural weathering test, ISO chemical 2810, Qualicoat) conversion >50 µm (ISO 2360) Layer thickness coating Coating weight 50 – 200 mg/m² Humidity resistance 1000 h at 40°C, 100% rH (DIN 50017 KK) GT0 after 168 h (Cross-Cut Test ISO 2409) Architectural / Building sector Building / Architectural Adhesion <5 mm (Cupping test, ISO 1520) 5-8 mm (Bend test, ISO 1520) Compatibility with a wide range of substrates and surface treatments such as Compatibility with substrate steel, Zn, hot dip galvanized steel (HDG), corrosion resistant steel (CRS, ISO 2409)
For architectural applications, in general products have to be in compliance with Qualicoat and the more demanding GSB specifications. Depending on the building materials, different specifications are applied. For coated aluminium (most commonly used), Qualicoat requires a corrosion resistance in acidic and neutral conditions of >1000 h according to ASTM B117 and ISO 9227. Length from scratch shall not exceed 16 mm²/10 cm. The GSB specifications also include the filiform corrosion test (EN 3665), where a minimum resistance of 1000 h with a GSB Factor lower than 0.4 is required. For Zinc-coated building materials, corrosion resistance in neutral conditions of >750 h according to ASTM B117 and ISO 9227 is necessary. Additionally, filiform corrosion test is required (EN 3665), where a minimum resistance of 1000 h must be achieved. For non-coated Zinc, where a chromium trioxide-containing pre-treatment is applied, a salt spray performance of >96 h (white rust) according to ISO 9227 is necessary. When using Cr(VI)-free pre- treatments, 48-72 h are sufficient to comply with current specifications. Blank Zn-coated steel must show corrosion resistance for 300 h according to ISO 9227. In addition to these standard requirements, in most national building codes it is common to refer to a minimal end-of-life period of about 20-25 years for most building materials. To check long-term performance of building materials, 1-10 years sea-side testing is required according to Qualicoat ISO 2810.
27 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Layer thickness is an important quality criterion in the architectural sector. This is measured by the analysis of the element concentration on the surface, which must be 5-15 mg/m² (measured by Atomic absorption spectroscopy (AAS) or colourimetric method). Adhesion is assessed according to ISO 2409, results must be GT0 after 168 h. Additionally, the cupping test (ISO 1520) must be performed, after testing the coating must not show any sign of cracking or detachment. Adhesion testing is of great importance to assess the compatibility with a wide range of substrates such as steel, Zinc, HDG or CRS.
3.3.3.2 Automotive sector Table 6 gives a short overview of selected quantifiable requirements of the key functionalities for the main process steps and post-treatments. The selection was made regarding the most relevant process related key functionality. A more detailed description is given in the subsequent paragraphs.
Table 6: Key requirements within the automotive sector
Process Quantifiable key functionality Requirements (on Al alloys)
48 h (CASS), ISO 9227) (CAA) Corrosion resistance >240 h (Neutral salt spray (NSS), ISO Chromic acid 9227) (Passivation) anodising (CAA) with subsequent Layer thickness <15 µm (ISO 2177) sealing after Simultaneous thickness and electrode anodizing Resistivity potential measurement (STEP, ASTM B Chromium trioxide 764) / chemical
Automotive sector Automotive Chemical resistance DIN EN ISO 20105 conversion coating No delamination (ASTM B533, TL 528, Adhesion ISO 1464) For surfaces treated by chromic acid anodizing, the automotive sector reported minimum requirements ranging from 48 h in the Copper Accelerated Salt spray (CASS) test to 240 h in the NSS according to ISO 9227. Specifications for anodized surfaces require a layer thickness <15 µm. For testing of resistivity, the STEP test according to ASTM B 764 is performed. Adhesion properties are assessed by the peel test according to ASTM B 764, TL 528 or ISO 1464 and no delamination of the layer should be observed.
3.3.3.3 Packaging industry Table 7 gives a short overview of selected quantifiable requirements of the key functionalities for the main process steps and post-treatments. The selection was made regarding the most relevant process related key functionality. A more detailed description is given in the subsequent paragraphs. Table 7: Key requirements within the Packaging industry.
Process Quantifiable key functionality Requirements
> 3 years, tests with simulants for performance Corrosion resistance evaluation while pack tests required with customers
industry Electrolytic Tests with simulants for performance evaluation, chromium coated Adhesion pack tests required with customers cross hatch to steel (ECCS) evaluate lacquer adhesion Pack tests required with customers visual Packaging Optical properties evaluation
28 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Process Quantifiable key functionality Requirements
Heat resistance >100 °C Food contact materials must not create any Food safety unacceptable risks for consumer of packed food
Electrolytic chromium coated steel (ECCS) For ECCS, the packaging industry reported that the surface has to resist corrosion for at least 3 years. Furthermore, lacquer adhesion is a crucial requirement, beside visual inspection of the optical properties. For evaluation of these critical endpoints, tests with simulants and pack tests required by customers are carried out. Moreover, coated materials have to withstand temperatures of at least 100°C for pasteurisation and sterilisation purposes. Food contact materials must not create any unacceptable risks for consumers of packed food. Therefore, tests with microorganisms certified by authorities have to be passed before a material is approved.
3.3.3.4 General engineering Table 8 gives a short overview of selected quantifiable requirements of the key functionalities for the main process steps and post-treatments. The selection was made regarding the most relevant process related key functionality. A more detailed description is given in the subsequent paragraphs.
Table 8: Key requirements within the steel processing sector
Process Key functionality Requirements On steel: Corrosion resistance 1000 h (ISO 9227) 350-500 h without delamination (EN 13523-8) < 1 µm (EN 13523-1), measurement of coating Layer thickness weight On steel: Adhesion with degree of delamination 0-1 (EN 13523-6, ISO 2409) Adhesion of subsequent layer on metallic chromium: Chromium trioxide Equal to chromium trioxide-based conversion / chemical coating (internal specifications) conversion coating on metallic chromium: Wear resistance Equal to chromium trioxide-based conversion coating (internal specifications) Chemical resistance > 100 MEK DR (EN 13523-11) In the current highly competitive market customers are more and more sensitive to (Thermo) Optical properties: aesthetic aspects. Candidates for substitution will Aesthetic/ brightness/ impression
General engineering (includingGeneral engineering steel) have to fulfil the same aesthetic criteria as the current chromium trioxide-based coating. Coating must resist to the working conditions in Corrosion resistance an electrical transformer i.e. T° up to 300°C (IEC 60404-1-1) Grain oriented steel insulation Layer thickness 3-5 µm (Permascope measurement)
Coating tension >4MPa
29 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Process Key functionality Requirements >3 MΩ/mm2 (normalized Franklin test, in Electric insulation compliance with standard CEI 60404-11). Surface uniform grey, without white spots (Thermo) Optical properties: Candidates for substitution will have to fulfil the Aesthetic/ brightness/ impression same aesthetic criteria as the current chromium trioxide-based coating. Corrosion resistance >1 year (no oxidation, visual inspection)
Heat resistance No oxidation after thermal cycle 2 h at 200°C
Conductivity No change of conductivity Passivation of
copper foil Application speed <20 seconds per dipping process
Compatibility with substrate copper foil has to be laminated on various resins
Layer thickness <0.7 nm
Chromate conversion coatings Regarding conversion coated surfaces on steel, industry stated minimum corrosion resistance of 1000 h according to ISO 9227 and ASTM B117. When corrosion performance is tested according to Salt Spray Test (SST) STN EN 13523-8, 350-500 h should be achieved and delamination should not exceed 2 mm at the vertical scribed mark. The layer thickness must not exceed 1 µm (EN 13523-1). Thickness is measured by an electrical probe placed on the coating, which develops an electromagnetic field in the base metal; analysis of the potential variation of this field can be used to estimate the film thickness. Alternatively, a measurement of coating weight can be performed. The adhesion properties are assessed by cross cut test according to ISO 2409 and EN 13523-6 and the degree of delamination should not exceed GT0-1. When tested on metallic chromium, adhesion properties and wear resistance must be equivalent to chromium trioxide-based conversion coating. Chemical resistance against solvents is tested according to EN 13523-11. Testing is performed by rubbing the coated surface with a tissue impregnated with a solvent (methyl ethyl ketone, MEK). Values are set in accordance with technical requirements, though a result > 100 MEK DR is desirable. Importantly, optical properties also play a crucial role. Customers in the current highly competitive market are very sensitive to aesthetic aspects. Consequently, candidates for substitution will have to fulfil the same aesthetic criteria as the current chromium trioxide-based coating.
Grain oriented steel insulation For grain oriented steel insulation, the industry reported coating tension as a key performance parameter. The tension imparted to the steel by the coating is related to magnetic properties. The coating tension must be >4 MPa, since a smaller tension leads to poor magnetic properties (core losses). Core losses are the most important parameter for this process. The steel sold to customers must have guaranteed magnetic properties which are in compliance with international standards - IEC 60 404, Epstein frame, and single sheet tester. The layer thickness also has a direct impact on the coating tension. Here, a thickness between 3 – 5 µm is desirable and is evaluated by permascope measurement. Deviations (too high coating thickness) lead to increased dust generation during slitting operation, risk of burr generation, and stacking factor (ratio between steel and coating which has to comply with IEC 60 404 standard). Laminations of electrical steel are stacked to form the iron core of electric transformators. Electrical insulation is provided mainly by the final coating. This is measured by a normalized Franklin test (in compliance with standard CEI 60404-11). Moreover, the
30 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES coating must be resistant to the working conditions in an electrical transformer i.e. T° up to 300°C according to IEC 60404-1-1. Importantly, optical properties also play a crucial role. Customers in the current highly competitive worldwide market are very sensitive to these aspects. If the surface is not uniform, the electrical insulation is not homogenious, resulting in current loss. Consequently, candidates for substitution will have to fulfil the same optical criteria as the current chromium trioxide-based coating.
Passivation of copper foils For passivated electrodeposited copper foils used in electronics, industry requires no oxidation after 1 year assessed by visual inspection. Testing of heat resistance is carried out, with a 2 h thermo-cycle treatment at 200 °C. No oxidation should be observed. Compatibility with different substrates is necessary, since the passivated cooper foil has to be laminated with various resins. Specifications for these surfaces require a layer thickness <0.7 nm and no change of copper conductivity should be observed. The material must be weldable, to prepare e.g. circuit boards. Regarding the scalability, passivation of copper foils is a high speed process, requiring a completed dipping in less than 20 seconds from roll to roll.
31 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
4. ANNUAL TONNAGE
4.1. Annual tonnage band of chromium trioxide The annual tonnage band for the use of chromium trioxide in surface treatment for miscellaneous sectors is <900 tonnes per year.
32 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
5. GENERAL OVERVIEW ON THE SPECIFIC APPROVAL PROCESS IN THE DIFFERENT INDUSTRY SECTORS
5.1. Architectural For architectural applications, a qualification program has to be passed by each process and product prior to implementation. Therefore, several national associations encompassing coaters of architectural parts formed a quality label organisation called Qualicoat in 1986 to provide best practice rules to obtain a good quality coating on aluminium. The following information is derived from www.qualicoat.net. Qualicoat is a quality label organisation committed to maintaining and promoting the quality of coating on aluminium and its alloys for architectural applications. To determine whether or not a coating meets a customer’s requirements, the results need to be measurable against technical specifications. Working on behalf of customers who have their products coated, Qualicoat defines comprehensive quality requirements and monitors their compliance by licensed plants worldwide. This gives purchasers of coated aluminium the assurance that they will receive a premium-grade product delivering long-term value and consistent quality. Qualicoat is committed in particular to: - establishing specifications for processes, products and tests to be used by the coating plants; - developing and improving these specifications; - granting licenses to coating plants that apply for the quality label; - testing and approving chemicals and coating products to be used; and - monitoring the correct application of the specifications in licensed plants. During previous years, Qualicoat raised and standardised the level of quality throughout Europe, laying down rules applying to different industries. Firms in many countries have become licensees, and Qualicoat has since grown on all continents. Through its efforts over the past 20 years, Qualicoat has played a key role in assuring the quality of aluminium parts used in architecture. The aluminium industry has been represented on the Qualicoat committees from the outset, thus ensuring an exchange of ideas and information between coaters and producers of semi-finished aluminium products. The Qualicoat quality label is a product certification scheme. Qualicoat has granted general licenses to national associations to issue these certificates and inspect the licensed plants. Tests are performed by laboratories recognised by Qualicoat and accredited to ISO 17025. These laboratories and the inspectors are bracketed together in Qualisurfal. Licensed coating plants who fail to meet the requirements lose their licence. Qualicoat has established specifications defining minimum requirements for plants and equipment, coating materials and finished products. All requirements in the specifications must be met before a quality label can be granted. The Qualicoat specifications and approval procedures for products have been modified over the last few years, but are essentially based on a variety of accelerated laboratory tests and limited period outdoor exposure testing. The most demanding tests are the acetic acid salt spray testing (ISO 9227) and the outdoor exposure testing. Additionally, stringent mechanical adhesion tests have to be passed. As stated during the consultation phase, many customers are very demanding with regard to performance of chromate-free alternative products. Therefore, there is an increasing demand for approval and certification by the GSB (GSB International, 2012, 2013), whose testing and approval regime is even more stringent than those of Qualicoat. The GSB assessment comprises the following four stages:
33 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
- Initial tests conducted by the applicant; - Laboratory testing and evaluation by a laboratory being approved by GSB (GSB is the first international organization for quality surface coating); - Pilot production testing at a company location approved by GSB, plus evaluation at a GSB approved laboratory; and - Outdoor exposure testing and evaluation for 36 months at an industrial marine environmental site. As mentioned, in addition to stringent mechanical adhesion tests and acidic salt spray testing for 1000 h, the Qualicoat and GSB approval both include a real-life test under harsh environmental conditions (sea-side conditions). Here, alternatives have to withstand outside marine environments in long term corrosion testing series that will take up to 10 years. The Qualicoat approval is often granted as preliminary approval while real-life long-term testing is outstanding. Nevertheless, manufacturers in the building sector generally have to give a >25 years warranty for the products, although, at the current stage, the chromate-free alternatives have not been tested for such a long lifetime. The Qualicoat approval as such is granted on test panels which are coated under clean lab conditions in the absence of interferences and so do not reflect industrial production conditions. Experience has shown that customers withdrew from alternative pre-treatments and went back to chromium trioxide- based conversion coatings, since real life performance was clearly not satisfactory. The majority of the alternative systems are potentially robust enough to meet even the long-term requirements of the architectural sector and are already applied successfully in many circumstances. In some countries (e.g. Spain), many architectural applications have been done on a chrome-free- basis for the last 10 years. However, annual evaluations worldwide showed that in the last 5 years the statistics of failures in salt spray testing were always in favour of samples treated with Cr(VI) by 2 to 7%. The reason for this is still unclear. Furthermore, for special, more demanding environments, it was recently reported that specific alternatives show an increased sensitivity to chloride salts: After 4-8 years, corrosion and adhesion failures were observed on buildings exposed to sea-side environments in the Netherlands. This is not consistent with the performance of these systems in Spain, where these failures were not observed. This effect may be correlated to the significantly more humid environment in the Netherlands, which, in combination with UV-radiation, leads to a much faster degradation of the lacquer system than in dry surroundings. Another limitation of these alternate systems is that they provide reduced protection with increasing amount of Cu/Fe in the Al alloys. Besides that, the aluminium industry is moving towards more recycling and the amount of alloying elements are changing. Therefore, several projects were initiated recently to deeper analyze these findings and to further develop alternative systems taking these potential issues into account. To date, companies clearly cannot always rely on accelerated test data from laboratory or first outdoor testing to substantiate the performance of a specific alternative product, as this was shown to result in many costly field failures over the last few years. Indeed, the alternatives are developed and adjusted continually, but the experience with the alternatives unadjusted in chemical composition and or in process circumstances is a maximum of 10 years. In the end, these data do not necessarily correlate to the ultimate performance of the coated surface over decades in a highly demanding seacoast environment or in proximity to other industrial sites such as power stations, oil refineries or chemical plants. Chromium trioxide-based coatings are a very tolerant system, while the alternatives are much more sensitive.
34 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
5.2. Automotive sector specific approval process 5.2.1. Current production parts in automotive applications - general considerations The automotive industry is a strategic industry in the European Union: 16.2 million cars, vans, trucks and buses were manufactured in 2012, employing 12.9 million people, including about 3 million high skilled jobs and having a turnover of about €840.5 billion (2011). Chromium trioxide is used by automobile supply chains to manufacture several thousand chrome- plated parts per vehicle manufacturer. Parts depending on the use of chromium trioxide cover a wide range of applications from belt locks to injector valves in vehicle models of a long production period of 7-10 years. Potential alternatives for chromium trioxide must be in compliance with the high demands and requirements regarding their critical performance properties within manufacturing processes and their final use. For these reasons, a simple 1:1 substitution of chromium trioxide is not possible. The identification of possible alternatives and the careful validation of their functionalities is a highly important and labour/time intensive process that will certainly take several years. 5.2.2. Current production parts - requirements for alternatives to chromium trioxide Chromium trioxide treated parts are unique amongst others in terms of corrosion resistance, hardness, layer thickness, adhesive strength, coefficient of friction, and abrasion resistance. Potential alternatives must be able to cover all of these requirements. A one to one substitution is not possible, and careful testing and evaluation of the alternative´s functional behaviour is needed. Current testing procedures include: laboratory tests, summer and winter tests, and continuous-operation tests. Thorough evaluation of possible alternatives is crucial to avoid failures in the field / daily application. Besides safety aspects, the consequences could otherwise be expensive and may include product recalls which are highly damaging to brands. A single vehicle is constructed from 4000 to 9000 different main components and assemblies. The range of different kinds of components is illustrated in Figure 9.
Figure 9: Car dismantled into constituent parts (Volkswagen AG, 2013) (left). Principal engine parts of a car (HubPages, undated) (right). If a substance has to be phased out or replaced, all affected components must be revalidated using suitable alternative materials. Even though the automobile industry is highly experienced in material testing procedures, the validation and testing of alternatives is unlikely to be completed before the sunset date, due to the sheer number of parts involved. This is especially the case because potential alternatives must be tested in terms of extension to large scale production and must be ready for use by the sunset date in September 2017.
35 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
The automotive industry considers the best course of action is a step by step introduction of alternative technologies in new type-approved models (Directives 2005/64/EC and 2009/1/EC), but this may not be feasible until the sunset date. However, to ensure production volumes of vehicles are not affected, sufficient capacity for the production of alternative coatings in Europe must be built up. Otherwise import from non-EU suppliers would be needed to bridge the supply gap. With EU based OEM´s using 70-80% EU suppliers (and non EU based OEM´s using 20-50% EU suppliers), a change to non EU suppliers would have a huge impact on the EU economy. With more than 10 million cars being built every year, building up sufficient capacity in Europe to cover all relevant parts is not possible by the sunset date. A further point is the high complexity of supply chains in the automotive industry. The assembly of vehicles is performed in a complex network of manufacturing plants, which form a multi-tier system producing different parts, such as exterior sheets or engines. With an average number of 1500- 4500 OEM suppliers, which have an average of 500-1500 suppliers themselves, tracking down chromium trioxide dependent parts is a time-consuming and complicated task. Lastly, the aforementioned multi-tier system, as well as the long-lasting life time of vehicles (up to 22 years and more) makes planning reliability crucial. Average life cycles of vehicles, are about 22 years and include 3-5 years development time, 7 years of production and at least 10 years of spare part guarantee. The opportunity to introduce changes is only possible within a certain period of time, which decreases rapidly after type-approval. Combining all these facts, the introduction of possible substitution parts has a long lead-time which cannot be met until sunset date (refer to Figure 10).
Figure 10: Typical life-time of a car model with start in production in 2018 compared with a four years period until sunset date (ACEA, 2013) The period to introduce changes decreases rapidly after type-approval by a certified body (Directives 2005/64/EC and 2009/1/EC). As shown in Figure 10, the period until sunset date (2013-2017) could appear in early stages of life-cycle but could generally appear at any stage of the minimum 22 year life-time of a car model, even during the spare part period when changes are no longer possible. 5.2.3. Past model service parts – general considerations The EU passenger car fleet consists of about 224 million vehicles. About 36 % of the overall number are older than 10 years (about 80 million cars).
36 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Figure 11: EU passenger car fleet (%s hare by age in 2010). Note: Information from 12 EU Member States where information was available (ACEA, 2013). The majority of European cars are removed from the fleet after 13 to 15 years. This underlines the importance of an efficient supply of past model service parts beyond the end of serial production. Apart from service considerations, national warranty obligations must be fulfilled. Therefore, a minimum of ten years availability of spare parts must be guaranteed (e.g. Germany: Civil law code §242). Commonly, past model service parts are provided for vehicles that have been out of production for more than 20 years. In general, shut-down of the production lines for several weeks are anticipated for process changes within this industry, e.g. transition from a chromium trioxide-based passivation to a Cr(VI)-free process. Industry reported during the internal consultation that production lines are used to capacity one year ahead according to contracts between the surface treatment company and the respective OEM. The annual maintenance shut-down, scheduled to take three weeks, is clearly not sufficient for transition to any alternative. Therefore, major changes of the process require a longer shut-down. As a consequence, the contracts between the plating company and the consumer / OEM cannot be fulfilled in the timeframe agreed and would finally be affecting the overall automobile supply chain. 5.2.4. Past model service parts – requirements for alternatives to chromium trioxide As mentioned, the interrelation of components in vehicles is highly complex and subject of thorough testing within the developmental phase of vehicles. Therefore, a one to one substitution of chromium trioxide is not possible. Substance substitution may cause change of function geometry, thermal durability and leads to unexpected impacts on related parts. To make sure that possible alternatives are interchangeable with original spare parts, a complete new type-approval is necessary. This may lead to major disadvantages, as discussed below. At the end of serial production, the tooling and bill of design for car model parts is transferred from a large main supplier to another supplier (usually a small or medium-sized enterprise (SME)) to ensure a sufficient spare part supply. These SMEs are able to produce the desired amount of past model service parts, using the original method. The limitation factor is that in most cases they do not have the know-how and capacity to perform costly and highly technically demanding re-development and re-validation procedures. A complete testing of all related components may be necessary to exclude unexpected impacts and to ensure functionality and safety in the field. Additionally validation processes must be based on the original vehicle, which may not be available in many cases. Another point is that due to the relatively small number of spare parts being produced in comparison to the high financial input needed for validation of alternatives, an enormous increase of price per item/part would occur.
37 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
The possibility of producing and stockpiling a sufficient amount of spare parts before the sunset date must be discussed. However, this alternative may have obvious drawbacks like negative impacts on functionality due to chemical aging, waste of resources if spare parts are not needed for past model services, as well as high demand of stockpiling capacities. In conclusion, the aforementioned arguments clearly show the need for chromium trioxide in past model service part production.
5.3. Packaging and food contact Articles intended for contact with foodstuffs have to meet a number of explicit requirements so that they can be used without any danger for the safety and quality of foodstuffs and the health of the consumer. In the assessment of food contact materials and articles, attention is mainly focused on the danger of food contamination with chemical substances present in the material the object is made from.
5.3.1. Food contact regulations in Europe New food packaging must comply with the EU requirements for food contact materials. Products that do not comply cannot be placed on the EU market. The requirements relate to materials and substances used, as well as the labelling on food contact materials. Food contact materials and articles are regulated by the following:
5.3.2. Framework Regulation EC 1935/2004 Regulation 1935/2004 aims at guaranteeing a high level of protection of human health and the interests of consumers with regard to the placing on the Community market of materials and articles intended to come into contact with food either directly or indirectly. It contains general requirements for all food contact materials:
Materials and articles which come into contact with food shall be produced in line with good manufacturing practice. They must under no circumstances transfer substances to the food with which they are in contact in quantities likely to: - endanger human health; - bring about an unacceptable change in the composition of the food; or - bring about a deterioration in the organoleptic characteristics thereof.
Legislation on specific materials Annex I of this Regulation identifies 17 groups of materials and articles for which specific measures may be adopted, amongst which metals and alloys and varnishing and coatings; These specific measures may include: - the list of substances authorised for use in the manufacture of materials and articles that are intended to come into contact with food; - criteria of purity; - specific conditions of use; - limits on the migration of certain constituents into or on to food; - provisions aimed at protecting human health or ensuring compliance with requirements for materials and articles that are intended to come into contact with food; - basic rules for checking compliance with the provisions above; - rules concerning the collection of samples;
38 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
- provisions for ensuring traceability; - additional provisions of labelling for active and intelligent materials and articles; - provisions concerning the establishment of a Community Register of authorised substances, processes, materials or articles; and - specific procedural rules for the authorisation of a substance, process, material or article.
5.3.3. Directives on substances Individual substances or groups of substances used in the manufacture of materials and articles intended for food contact are also regulated. For example, the Regulation 1881/2006 sets maximum levels for certain contaminants in foodstuffs, including inorganic tin.
5.3.4. National legislation In the absence of specific measures adopted at EU level, Member States may maintain or adopt national provisions for groups of materials and articles. Countries that have reportedly introduced national legislation potentially impacting metal packaging are: - Czech Republic: Decree No. 38 of 2001 covering elastomers and rubber, paper and board, metal and alloys, wood, cork, varnishes and coatings, printing inks, glass and enamel; - Belgium: the overarching legislation regulating food contact materials and articles, which is currently undergoing revision, is the Royal Order of 11 May 1992. This law sets specific requirements for certain food contact materials, but not for coatings. Project of transposition in national law of the Resolution ResAP (2004) concerning varnishes and coatings intended to come in contact with foodstuff; new draft legislation that proposes to regulate food contact coatings for the first time; - France: Decision of 28/06/1912, Decision of 15/11/1945, Decision of 13/02/1976 and Decision of 27/08/1987 on metals and alloys; and Decision of 02/01/2003 on plastics, varnishes and coatings; - Greece: decision No. 446/98, Greek Food Code, Article 28 on coatings; and decision No. 232/98, Greek Food Code, Article 22 on metals, cans and alloys; - Hungary: 17/1999. (VI.16.) EüM Regulation on forbidden usage of lead, cadmium, zinc and brass as food contact materials. Limitation of nickel and copper and copper alloys for enamels and metals; - Italy: Decree of the Ministry of Health of 21 March 1973, as amended, on plastic, rubber, paper, glass, stainless steel and tin; - Lithuania: Ordinance No. V-371 of 2006 on paper and board and metal; - Slovakia: Decree No. 1799 of 2003 on Elastomers and rubber, paper and board, glass, metal and alloys, wood, cork, textile products, varnishes and coatings; - Spain: Resolution of 4/11/1982 on polymers and the country has recently updated its coatings legislation with the enactment of Royal Decree 847/2011; - Sweden: Decree No. 2005:20 on lead and cadmium in equipment used when handling foodstuffs (other than ceramic articles); and - The Netherlands: Dutch Packaging and Food Utensils Regulations under the Commodities Act (Warenwet) on ceramics, coatings, glass, metals and alloys and paper and board. Ongoing amendment. Most extensive EU MS requirement for food contact coatings.
The Council of Europe has adopted a Resolution on Metals and Alloys in Contact with food that will likely be adopted as a method of demonstrating that a material complies with Article 3 of Regulation 1935/2004. Several countries have already informed their intention of adopting the Resolution into their national law.
39 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
5.3.5. Other food contact regulations To be able to export materials, empty, or filled packages to non-EU countries, these need to comply with local regulations. Several such national regulations exist on food contact materials. In addition, food companies often have their own internal standards, which can be based on the legislation of their country of origin. For many regions and market parties, the food contact regulation of the USA serves as the guiding regulation. Hence, approval by the US Food and Drugs Administration (FDA) is an important benchmark for food contact materials.
5.3.6. Authorisation of new substances on the EU market In case an alternative for the manufacture of materials or articles intended to come into contact with food involves a substance that has not yet been recognized for its absence of adverse effects (when it comes into contact with food, and the possible migration of this substance into the foodstuff media), it may be necessary to apply for an authorisation of such substance. In such case, the application shall be made to the competent authority of the Member State where the substance is to be placed on the market and regulated. Specific marketing requirements for metal packaging are not harmonised at EU level as yet and thus, in addition to the general safety requirement in Regulation 1935/2004, national legislation must be complied with.
5.3.7. Development of suitable alternatives Introducing new materials into the packaging steel market is a complex process, involving multiple phases and checks. Canned food can be stored over years without compromising the safety of the contents, a factor which determines its position in many markets. The canning industry is capable of processing large quantities of produce in short time during harvest periods and delivering these products over a longer time period to consumers. In doing so, the canning industry is capable of absorbing differences in harvest yields, due to seasonal influences and spreading products geographically over the world. Other packaging is less capable of long shelf life, and lacks the flexibility in supply that cans deliver. Typical storage times are 3 to 5 years. The longer shelf life is usually for products that have large variation in supply over years. An example of such a product is canned salmon, where in poor years yields can be as low as 30% of average and in good years as high as 200%. These variations can only be buffered by keeping large strategic stocks over a long time.
5.3.8. Testing requirements Shelf-life needs to be ideally tested in real-time up to three years (in some cases according to a major can making company it can take up to five years) and the testing involves filling the cans, storing at ambient and elevated temperatures and carrying out an examination of them every 6 months. This is done by the can-makers and some large fillers. Faster test methods than real-time real-conditions testing raise the holding temperature, but only to a limited extent as elevated temperatures induce different chemical reactions in food, thus leading to different failure mechanisms. Testing with simulants is another option, but again, this will often show different failure modes and cannot provide the assurance that a certain packaging is safe. Both accelerated testing and food simulants can be used in the early stages of development, when the key interest is to discriminate between systems and determine relative performance. However, they should always be complemented by normal conditions testing (“direct determination”), as it is not possible to predict the storage performance of a product under normal conditions from its
40 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES performance when “abused”. Each time judgments of this type are made can-makers run a risk of making an error which could affect their customer’s products and impact upon their reputation.
5.3.9. Technology readiness levels in the food packaging sector The development risk is managed by a development process differentiated into phases, bringing the material step by step to application in the market. Going through these steps, the risks are reduced while financial commitments increase. A multi-phased approach allows weak solutions to fail fast and to grow market commitment while developing a successful product. Analogous to the concept of Technology Readiness Levels (TRLs) in the aerospace sector, the following stages of readiness levels are defined for the development of a suitable alternative to chromium trioxide in the food sector. These readiness levels are used to assess the maturity of evolving technologies during their development and were developed by NASA (National Aeronautics and Space Administration) in the 1980s.
TRL 1 to TRL 4: Screening phase - from basic principles to laboratory testing The aim of the screening phase is to investigate many alternatives and quickly evaluate their relative performance. Alternatives can originate from many sources: literature studies, patent examinations, existing solutions in other areas, supplier alternatives, competitor analysis, etc. In the laboratory-screening phase the variance is still large, and results therefore are only indicative. Throughput time for producing and testing a sample is in the order of weeks; there is no specific overall throughput time for the screening phase as it varies largely with the number of alternatives tested. Multiple iterations are often needed before a promising set of alternatives is defined after having passed the test requirements at this stage. Samples are produced with simple tools in this phase. As a consequence, product variation can be large, which is addressed by testing multiple products, ignoring the extremes and using the average of the remaining samples. This allows no detailed but a rough comparison of the tested alternative systems. The testing of samples is done according to several standardized methods. First, the quantity of the active substance is measured, then performance is checked by some relevant analytical methods. The current product is often incorporated in the testing as a reference in order to compare samples that are produced in different laboratories or at different times. For some critical testing, round robin testing may be used to determine variations between laboratories. For passivation on tinplate, a standard set of tests is defined on a score card. The specific product parameters are described therein with the required test method. Scoring is done on a 5-point scale against the reference chromium trioxide passivated product (311); much better (5) /better (4) /equal (3) / less (2) / much less (1). Adding all scores provides a relative score for each alternative, which can be used to decide on whether to enter the next phase or restart the process.
TRL 5: Component validation in relevant environment Alternatives that revealed good performance in the screening phase need to be produced in representative quantities and tested under relevant environmental conditions. The application process also needs to be evaluated and judged with respect to larger scale production. This is conducted by producing more trial material, either on existing trial equipment or by an improvised set-up on a production line.
41 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
The typical overall time of TRL 5 is a minimum of 2 years and can be longer if more variants are involved or other complicating factors, like seasonality of the products, are involved. The aim of the process upscaling trials is both, to retrieve larger quantities of trial material and to test the application technology that will be needed to produce the new material. Introducing a new material usually involves altering the production equipment, which requires careful planning of activities to implement on an existing and running line. Regular maintenance intervals are often used to prepare for tests, so timing of tests is critical. When new or modified hardware is needed, there will be a lead-in time of several months to engineer and order equipment. Product verification: As larger quantities of material become available, it is possible to complement the laboratory testing with an initial full application trial of the material. Cans will be produced for this purpose, which will undergo full processing for a number of relevant applications. After filling, these cans will be stored under controlled conditions and samples will be taken at regular intervals to assess the performance; usually by means of visual inspection. For practical reasons, these tests are limited to 1 year, though additional cans will be occasionally used to continue the test after that period. In addition, multiple cans are needed during TRL 5 to eliminate variances in application methods and canmaking.
TRL 6: System/subsystem model or prototype demonstration in a relevant environment When sufficient process knowledge is available and performance of the product has been proven including TRL 5, the next phase is to convert or build one line, and obtain operational experience. In a demonstration line, it will be possible to make larger runs to determine the long-term stability of the process and to produce larger amounts of material, which is representative to future deliveries. Initially, production of the demonstration line is limited to a few runs or batches, which is gradually increased to continuous operation (if production results meet the requirements). Engineering a demonstration line takes 3 to 6 months; building or converting a line will usually take 6 (conversion) to 18 (newly build) months, while increasing production to continuous operation may involve 3 to 12 months. Process verification: A demonstration line is engineered with some spare capabilities to be able to fine tune and optimise the process and to operate in a wider operating window compared to the narrow one under the improvised conditions of the upscaling trials. Production speed is increased, production runs are extended to longer runs and the product flexibility operation is improved to cover the full range of the product. This may lead to a more detailed process description and refined process control. The demonstration line is also the stage where the monitoring and quality control of a new process is developed. This can only be done when robust equipment is available. The larger volumes of product that are available from a demonstration line and especially the improved quality will enable customers to run product qualifications. The qualification process is typically a three-step process of trialling a new material on all aspects of canmaking, filling and processing. The ideal case is that the new product will be a drop-in replacement for the traditional product, without the need to change any of the production steps. In the real world, however, issues are likely to occur that will need to be addressed, either by a specification change of the material, or by alterations to the process settings (tools or otherwise). Regarding passivation, the most likely changes are related to the lacquering, as adhesion is determined by the interactions on the surface of the material. Normal qualification steps will consist of 1) single supply unit, typically a coil of 10 tons, 2) a small series of coils, typically five coils and 3) the regular supply quantity, typically 100 tons. First qualification steel will involve full testing of the products. On
42 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES positive results, subsequent phases will involve less thorough testing and more rely on comparative checks against the approved batch. A successful qualification step will typically take a total of 14 weeks which is compiled of 9 weeks order lead time, 1 week delivery; 4 weeks throughput time for canmaking time, plus the relevant shelf life of the packaging to be made.
TRL 7 & 8: Prototype & actual system completed and 'qualified' through test and demonstration In the final phase of material development the new process is implemented on all production lines. Experience obtained from the demonstration line is valuable and can be used for the process implementation. The focus in TRL 7&8 is on integrating the new technology in the existing configuration, specific engineering requirements, order time for components, and installation time. New equipment is always pre-assembled off line and installed during a planned maintenance stop. Typical packaging steel coating lines have quarterly short maintenance stops (days) and one annual long maintenance stop (1 week). Combining installation of new equipment with maintenance is common practice. Product homologation: Once a line is running a new process, final testing determines if the material complies with all specifications. This is conducted by means of laboratory analysis of the material. Functional testing by end users is not needed if the material is already qualified. For very critical customers, products or end uses, a line-specific requalification may be required.
TRL 9: Actual system ‘proven' through successful operations As described, the introduction of new material in the mature packaging industry is a multi-phase activity with a total throughput time of many years. This is illustrated by the activities of the industry over previous decades. Although developing alternative passivation systems has been ongoing since the early 90s on a worldwide scale, the most promising alternatives being currently investigated are in the phases of upscaling trials to process verification in demonstration lines. If these efforts are successful, the process to find a general replacement for chromium trioxide will need multiple years. Major show stoppers or severe issues related to either performance or food safety or lacquer compatibility will further delay the time to develop a solution to an established product for several more years. Shelf-life tests need to be performed after a final decision has been made on selecting the preferred Cr(VI)-free alternative solution and the applicants are able to supply new material at the industrial scale. When an alternative solution is agreed upon and following conversion of the tin lines, the tin plate material will have to undergo testing and qualification by can-makers and can-fillers to ensure conformance with the specifications for each application and more specifically to establish that the new materials meets the shelf-life requirements.
5.3.10. Summary of timeframes In order to meet production speed and prevent non-conformity of the quality of the products, guidelines exist for the food sector to manage manufacturing risk and technology transition processes. Analogous to the aerospace sector, manufacturing processes require stable product technology and design. The final level (Manufacturing Readiness Level (MRL) 10) represents full rate production and is reliant on achieving TRL 9.
43 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
5.4. General engineering Chromium trioxide is used for several processes for general engineering in thousands of different products. In addition to trucks, forklift trucks, and agricultural equipment, functional chrome plated products are used in thousands of different complex machines. They are in general produced by several thousands of different SME coating companies, who do this as contract manufacturers. In practice, these companies are not technically able to develop and introduce new coatings, because they do not know all the properties that are needed in all different applications. Additionally, the technical expertise and workforce are not available. Furthermore, developing new coatings is time consuming and a costly affair. Although smaller companies such as engineering companies, coaters, etc. would be willing to develop alternative coatings, they could not cope with the consequences should a new coating fail after upscaling production. This exceeds the entrepreneurial risk of smaller companies. New general developments and introduction of new coatings must be provided by major companies (while being supported by the formulators) from the respective industry sector. The approval process is quite similar to the automotive industry, the same approval time can be estimated. After the engineering companies (who are the decision makers), have agreed on a new coating, it takes at least 3 to 5 years to introduce all new equipment to the SMEs for production to begin. The shortest timeframe for a real introduction of a new coating is 10 to 15 years for the general engineering sector, due to inherent high risks and the wide variety of products.
44 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
6. IDENTIFICATION OF POSSIBLE ALTERNATIVES
6.1. Description of efforts made to identify possible alternatives To prepare the authorisation of chromium trioxide, the industry consortium CTAC (Chromium Trioxide Authorisation Consortium) of 150+ members was launched in 2012. The aim of CTAC was to efficiently gather and analyse all necessary information for the three pillars of the authorisation dossier (CSR, AoA, SEA).
6.1.1. Research and development As mentioned earlier in this document, a large amount of research over the last few decades has been commissioned to identify and develop viable alternatives to chromium trioxide. The unique functionalities of chromium trioxide (explained in detail in chapter 3.3) make it challenging and complex to replace the substance in surface treatment applications where superior corrosion or adhesion properties are required to ensure safe performance in a demanding environment. Most of these projects are conducted in the aerospace industry, e.g. research programmes funded by Europe clean sky (MASSPS, ROPCAS, LISA, DOCT) as well as programmes funded by United States Air Force (USAF) or other national funded programmes (e.g. LATEST in UK). Indeed, information from these projects are instrumental for other industry sectors as well. Some of these activities are described below in more detail. Amongst a number of initiatives in that respect, the Airbus Chromate-Free (ACF) project was launched more than 10 years ago with the aim to progressively develop new environmental friendly Cr(VI)-free alternatives to qualified products and processes used in aircraft production and maintenance. Even prior to the launch of ACF, R&D efforts included the objective to remove chromium trioxide use. The ACF project is organised into several topics for the different fields of technologies concerned by the replacement. ACF specially addressed applications where chromium trioxide are used in production or applied to the aircraft; such as CAA, basic primer, and external paints. In addition, bonding primer, jointing compounds, pickling, sealants, chromium-based chemical conversion coatings, passivation of stainless steels, passivation of metallic coatings or alternatives to hard chromium are included in the remit of this project. In synergy with ACF, an Airbus Group chromium trioxide replacement project is also in place. In 2006, Boeing in cooperation with the Department of Defence started a three-year program called “Environmentally Benign Coating System for Department of Defence Substrates” for the development of new chromium trioxide-free coating systems, based on rare-earth conversion coatings. Industry is not only working on one-to-one replacements for Cr(VI) applications, but is also reconsidering whole current coating systems. The large investment in innovative coating technologies may lead successively to a paradigm shift within the next decades. As an example, the HITEA (Highly Innovative Technology Enablers for Aerospace) project was initiated in 2012; a 17-member consortium consisting of aerospace OEMs, suppliers, paint application companies and academics with the goal to identify and evaluate suitable alternative systems. In 2014, the tested alternatives are planned to reach TRL2. After the initial phase, the project will focus on a handful of promising alternatives, where further testing will be undertaken within the next years. Completion of the research project is planned for 2015. Qualification (TRL6) will take up to 5-8 years from now. In 2008, the multi-company project SOL-GREEN was initiated for the development of protective coatings of Al/Mg alloys (Cerda et al, 2011). Since these coatings solutions are not based on
45 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
electrochemical conversion, and so require a complete change in technical approach, the industrial production qualification is expected not before 2025. Phase 1 was finished last year, showing that SOL-GREEN 1 faces some technical issues. Therefore, the main objective of SOL-GREEN 2 is to assess and develop an electrophoresis process to apply the anti-corrosion coatings using a SOL-GEL technique for complex geometry parts. These challenges are currently ongoing and the research is mainly conducted at laboratory scale (TRL2) at universities and in some partner’s plants. However, as mentioned above, this is a long term solution (10-15 years). The R&D project IPSA launched by the European Commission and the General Directorate for Research and Innovation aimed at the development of alternative packaging steel as alternative for ECCS. The project was finalized in 2013 and documented with a report of Marmann et al. (2013). The project showed reasonable results for non reflown tin steel (NR-TLS) for lacquered applications. For both application types, lacquer coated and polymer coated, further R&D is necessary either to improve the performance (NR-TLS for lacquered coatings) or for an overall alternative for polymer coatings. Although LTS is a promising concept, it will not be a general alternative to ECCS for all kind of applications (for example not for the beverage industry due to the presence of tin).
6.1.2. Data searches For the analysis of alternatives, extensive literature and test reports were provided by the technical experts of the CTAC consortium members. Furthermore, searches for publically available documents were conducted to ensure that all potential alternate processes to chromium trioxide-containing applications were considered in the data analysis. In addition to databases for scientific literature, the following programmes were intensively consulted: Toxics Use Reduction Institute, Massachusetts, US (www.turi.org/); The Advanced Materials, Manufacturing, and Testing Information Analysis Center (AMMTIAC: http://ammtiac.alionscience.com/). Searches for safety data sheets (SDS) for Cr(VI)-containing and chromate-free applications were also conducted. Based on these data, primary scoping led to the development of a generic questionnaire containing potential alternatives to chromium trioxide-based surface treatment processes. As a result of this, additional alternate processes, mentioned by companies from the CTAC consortium were included in the initial list of alternatives, which can be found in Appendix 1.
6.2. Consultations A questionnaire was provided to all CTAC Consortium members to get an overview of and experience with the alternatives, completeness and prioritisation of critical parameters for their specific processes and the minimum technical requirements. During this survey, additional alternatives have been identified which were included into the aforementioned initial list. At this stage of the data analysis, several alternatives had been screened out after bilateral discussions with the companies, based on confirmation that they might be general alternatives to chromium trioxide-based processes (e.g. for functional chrome plating), but are not applicable for the use defined here. To verify data and obtain more detailed quantitative information, further focused technical questionnaires were sent out and discussed with the CTAC consortium members. In addition, site visits to selected companies were carried out. These were carefully chosen to adequately represent the different uses, industry sectors, countries and the size of companies. Discussions with technical experts followed by a final data analysis led to the formation of a list of alternatives divided into 3 categories, according to their potential to be suitable for the specific use.
46 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
The most promising alternatives within the here defined use (category 1 and 2) are assessed in detail in the following chapter. Category 3 alternatives are summarised in Appendix 1.
6.3. List of possible alternatives The most promising alternatives are discussed in the following chapter. To allow a better overview of the different parts of the process chain, the assessment is made for main treatments plus post- treatments (Table 9) and pre-treatments (Table 10) separately. The main and post-treatment alternatives are classified according to their relevance; as Category 1, highlighted in yellow (focus of CTAC members, relevant R&D on these substances ongoing) or Category 2, highlighted in red (discussed mainly in literature, clear technical limitations, may only be suitable for other industry sectors or for niche applications but not as general alternative). Category 3 alternatives, which are not applicable for the use defined here, are summarised in Appendix 1.
Table 9: List of main treatment alternatives categorised (Category 1, highlighted in yellow; Category 2, highlighted in red)
Application with Definition Industry sector
General Passivation of copper foils PVD Engineering Silane/Siloxane, Automotive Cr(III) sol-gel coatings Organometallics Silane/Siloxane, Manganese- (Zr-/Ti-based) sol-gel coatings based processes Chemical conversion coating (CCC) Architecture Acidic surface Molybdenum- Cr(III) treatments based processes General Organometallics 5-methyl-1H- Cr(III) engineering (Zr-/Ti-based) benzotriazol General Other oxide- Grain-oriented electrical steel insulation Cr(III) engineering based coatings Low tin steel LTS with Electrolytic chromium coated steel (ECCS) Packaging (LTS) Silane/Siloxane Acidic surface Silane/Siloxane, Automotive Chromic acid anodising (CAA) including treatments sol-gel coatings subsequent sealing Acidic surface Architecture treatments
Table 10: List of pre-treatment alternatives categorised.
Alternative Surface pre-treatment Substrate
Functional cleaning/ Aluminium and aluminium alloys, Pickling/Etching/Desmutting Steel, copper, brass, molybdenum Deoxidizing Aluminium and aluminium alloys Inorganic acids (plus additives) Stripping of inorganic Aluminium and aluminium alloys finishes Stripping of paint Magnesium and magnesium alloys Aluminium and aluminium alloys, Hydrogen peroxide activated benzyl alcohol Stripping of paint steel (CRES), nickel/cobalt alloys, (with acids) titanium and magnesium
47 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES In the following chapter, possible alternatives are assessed specifically for the industry sector, where they may be potential replacements. Initially, general process or substance properties are described, followed by the assessment of the technical feasibility. In this chapter, the assessment is made separately for every industry sector in which it may be suitable. Also, in the chapters Availability and Conclusion, the assessment is done on a sector specific basis. To assess the feasibility of the alternatives, colour-coded summary tables are included in the document. The colours are as follows: - Red: not sufficient - the parameters/assessment criteria do not fulfil the requirements of the respective sector; - Green: sufficient - the parameters/assessment criteria do fulfil the requirements of the respective sector; - Yellow – the parameters/assessment criteria fulfil some requirements for some but not all applications/sectors (only used for the assessment of the technical feasibility).
The alternative assessments each comprise a non-exhaustive overview of substances used with the alternatives and alternative processes as well as the risk to human health and environment. These tables are provided in Appendix 2.
7.1. Main processes & post-treatments
CATEGORY 1 ALTERNATIVES The alternatives assessed in this section are considered the most promising ones, where considerable R&D efforts are carried out within the industry. Category 1 alternatives were often discussed during the consultation phase. In most cases, they are in early research stages and still showed technical limitations when it comes to the demanding requirements from the different industry sectors, such as corrosion performance. However, some of these possible alternatives may already be qualified and used in other industry sectors or for niche applications, respectively for single process steps of the process chain within industry but not as general alternatives to chromium trioxide-containing surface treatment process chains.
7.1.1. ALTERNATIVE 1: Acidic surface treatments 7.1.1.1 Substance ID and properties A variety of inorganic acids and organic acids (tannic, citric, tartaric) are currently under evaluation as alternatives to chromium trioxide in surface treatment processes within the applied use. Research is currently focused on boric acid, sulphuric acid, phosphoric acid, tartaric acid, nitric acid and citric acid. Table 11 provides an overview of which acids are used in the respective surface treatment processes. The most important processes, where inorganic acids are used, are anodizing coating processes of aluminium and magnesium, conversion coating processes of aluminium, zinc, zinc-nickel, cadmium, magnesium and silver, and passivation processes of stainless steel for creating stable oxide coatings, converted oxide layers, or passive films. Ferrous metals like iron or certain steels may cause interferences with subsequent coatings or platings and are therefore considered with alternative methods.
48 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
An overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.1.
7.1.1.2 Technical feasibility Table 11 summarizes chromium trioxide-based surface treatment processes where inorganic and organic acids were assessed to be an applicable alternative.
Table 11: Overview on the acids used in the different surfaces treatment processes
Industry sector Surface treatment Substrate / coating Alternative
Chromic acid Aluminium and Automotive Sulphuric acid anodizing (SAA) anodizing aluminium alloys Aluminium and Chromic acid aluminium alloys, Zn- Sulphuric acid anodizing (SAA) anodizing Architectural coated steel industry Aluminium and Chemical conversion aluminium alloys, Zn- Tannic acid coating coated steel
7.1.1.2.1 Architectural industry
Chromic acid anodizing General assessment: It was reported that with painting as post-treatment, anodizing with inorganic or organic acids (such as SAA) and conversion coatings based on these acids are in line with the main specifications from Qualicoat and GSB. SAA is already implemented into Qualicoat specifications. It produces a colourless, transparent anodic coating on most aluminium alloys. Generally, Cr(VI)- based-coatings are visible, which is currently preferred to ensure that a visual inspection of the effectiveness of the process can easily be made. However it was stated that visibility or not should not be an issue since several other methods exist to inspect the effectiveness of the coatings. Companies mainly apply CAA to high performance parts in the building sector. In that case, the specific requirements for these high performance applications cannot be met with inorganic or organic acids as alternative in the anodizing processes. Corrosion resistance: It was reported that if treated products are painted, the corrosion performance of aluminium substrates anodized with inorganic or organic acids is in accordance with the standard Qualicoat requirements. Specifications ask for 1000 h in an acidic salt spray test according to ISO 9227, while zinc coated steel surfaces can reach the required 500 h. As stated above, CAA is generally used for some special applications with higher requirements (NSS, AASS 2000 h, < 2 mm). For these special applications, the alternative treatments are clearly not sufficient. Adhesion: In laboratory tests, the required grading of GT0 according to ISO 2409 can be reached. Layer thickness: Sulfuric acid anodized coatings for exterior building products are much thicker than chromic acid-based ones. Here, a thickness of >18 µm is needed to withstand continuous outdoor exposure. This range of coating thickness is not suitable for highly specular (bright) finishes. Most applications are matte finished. Long-term experience: In addition to stringent mechanical adhesion tests and acidic salt spray testing for 1000 h, the Qualicoat and GSB approval systems both include a real-life test under harsh environmental conditions (sea-side conditions). Here, alternatives have to withstand outside marine environments in long term corrosion testing series that take up to 10 years. To date, companies clearly
49 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
cannot always rely on accelerated test data from laboratory or first outdoor testing to substantiate the performance of a specific alternative product, since this has been shown to result in many costly field failures over the last few years. The alternatives are developed and adjusted continually, but the experience with the alternatives which are unadjusted in chemical composition and/or in process circumstances, are a maximum of 10 years. In real life, these data do not necessarily correlate to the ultimate performance of the coated surface over decades in a highly demanding seacoast environment or in proximity to other industrial sites such as power stations, oil refineries or chemical plants. Chromium trioxide-based coatings are very tolerant systems, while the alternatives are much more sensitive. Conclusion: To date, surfaces anodized with inorganic or organic acids cannot be seen as a 1:1 replacement for chromium trioxide-based coatings. Although standard corrosion requirements can generally be met, CAA was reported to be mainly applied in special applications when a higher performance is mandatory. For these applications, the alternatives do not fulfil the more demanding requirements. Most importantly, although current products are approved by Qualicoat or GSB, no long term exposure data in real-world environments exist. Since failures have arisen from the industrial use of replacement products within the last years, doubts remain on the ultimate performance of surfaces anodized with inorganic or organic acids.
Corrosion resistance Adhesion Robustness Long-term experience
Not for High performance
parts
Chemical conversion coating General assessment: First proprietary preparations based on tannic acid as possible alternatives for the treatment of aluminium were developed in 1999. With this treatment, a coloured coating is achieved which is generally preferred by customers, enabling visual assessment of the effectiveness of the process. Qualicoat approval was first granted more than 10 years ago, with a modified formulation following in 2009. At the current stage, the approval is expired and so far has not been renewed. Corrosion resistance: First products based on tannic acid were granted Qualicoat approval in 2003, laboratory and short-term outdoor testing in seaside and industrial environments passed the standard requirements for corrosion resistance of Al panels. Adhesion: While in laboratory tests the requirements of Qualicoat in accordance with ISO 2409 could be fulfilled, industrial scale up showed severe problems with paint adhesion of tannic acid treated surfaces. Robustness: As a clear disadvantage, the tannic acid-based process needs an even more stringent process control compared to chromate conversion coating and other chromate-free alternatives, such as titanium or zirconium-based conversion coatings (chapter 7.1.6.2.1). It was stated that first tannic acid conversion coatings caused significant blistering during salt spray exposure in a pilot test series. Most likely, water quality has a great impact on the performance of the treatment. After approval in 2003, the product was tested under industrial conditions. Here, the process showed clearly insufficient performance. Failure of mechanical testing occurred due to inappropriate paint adhesion and inefficient drying. In contrast to chromium trioxide, tannic acid does not provide etching capabilities and the treated surfaces need complete drying, rather than just draining, before they can be further processed. Moreover, adaptation to existing process conditions was stated to be an issue, beside discolouration of subsequent paint. Current modified processes are reported to be more stable against contaminations within the process. However, this has to be evaluated in large scale tests.
50 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Long-term experience: Beside stringent mechanical adhesion and acidic salt spray testing the Qualicoat and GSB approval both include a real-life test under harsh environmental conditions (sea- side conditions). Here, alternatives have to withstand outside marine environments in long term corrosion testing series that take up to 10 years. No evaluation of long-term performance has been performed so far. Conclusion: Tannic acid conversion coating for the treatment of aluminium is technically no alternative as the robustness of the process is currently not sufficient for the architectural sector. Industrial scale up showed severe problems with paint adhesion. Furthermore, no evaluation of long- term exposure in demanding environments has been performed so far.
Corrosion resistance Adhesion Robustness Long-term experience
7.1.1.2.2 Automotive sector General assessment: The automotive sector is using CAA on aluminium for a wide variety of components (e.g. bumpers, cylinder heads, wheels, gear box housings). During the consultation it was stated that the inorganic or organic acids are not in line with current specifications and are not seen as suitable replacements for the automotive sector. Corrosion resistance: When CASS is applied according to ISO 9227, most of the tested inorganic and organic acids showed clearly insufficient performance on aluminium (< 8 h). Only SAA gives sufficient protection against corrosion on high purity aluminium (24 h). Its specific porous surface structure makes it ideal for colour finishing. The process is already qualified for some applications within other sectors. Layer thickness: Most importantly, to achieve the required corrosion resistance, the layer thickness is significantly higher (10-15 µm) than for CAA (specifications claim 2-7 µm). As a consequence, this procedure cannot be applied to parts with low manufacturing tolerances. The higher thickness leads to a significant reduction of the fatigue strength, since CAA is much more ductile, which is a crucial requirement for structural parts. Adhesion properties: During the consultation, it was confirmed that in addition to the abovementioned criteria, other key parameters such as adhesion requirements are currently not met by the alternative. Conclusion: In summary, the anodizing process with inorganic or organic acids might be used as replacement to CAA for specific applications. However, the here described processes are clearly not meeting the requirements for fatigue-sensitive parts, since the corrosion resistance and layer thickness as crucial performance parameters are insufficient. While for SAA the corrosion resistance might be sufficient in CASS, the higher layer thickness does not meet the requirements from the automotive sector.
Corrosion resistance Adhesion Layer thickness Fatigue strength
Only SAA sufficient
51 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.1.3 Economic feasibility Against the background of significant technical failure of these alternate systems, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible.
7.1.1.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. In case of sulfuric acid, the substance is classified as Skin Corr. (skin corrosion) 1A and Met Corr. (substance or mixture corrosive to metals) 1. Tannic acid is classified as Eye Irrit. (Eye irritation) 2, Aquatic Chronic 3, Skin Irrit. (skin irritation) 2. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of the above mentioned alternatives would constitute a shift to less hazardous substances.
7.1.1.5 Availability Architectural sector: SAA is already approved and available as anodizing alternative for applications requiring Qualicoat specifications. However, customers mainly apply conversion coatings for exterior building parts. Anodizing with chromium trioxide is carried out for special high performance parts in the building sector. Although not in the main focus of the architectural sector, R&D on improved performance on inorganic or organic acids as alternatives to chromium trioxide is currently ongoing. A lot of R&D has been performed within the last decade on tannic acid-based alternatives for architectural purposes. A first tannin-based product was developed for Qualicoat evaluation in 1999, Qualicoat approval was granted in 2003 upon successful completion of the laboratory evaluation. A modified tannic acid-based product passed Qualicoat evaluation in 2009. However, due to several issues arising during upscaling, approval expired without being renewed so far. Currently, R&D is ongoing to improve the formulation and to overcome the previous problems. It is foreseen that a new modified tannic acid type alternative will be submitted for GSB and Qualicoat approval. Approval could be granted within the next 5 years, if no major drawbacks occur. Thereafter, industrial upscaling is anticipated to take several years, including further outdoor testing, to ultimately assess the alternative. Automotive sector: From the tested chromate-free anodizing alternatives, only SAA was transferred to further R&D testing, while other acidic anodizing treatments were clearly found to be not suitable for automotive applications. Investigations of SAA are ongoing at laboratory scale. If these tests are successful, extensive outdoor testing will have to be carried out to assess the quality and functionality of new coatings in real-life conditions. However, for final analysis before implementation, long-term field experience is mandatory. The products for the global automotive market, especially exterior parts, have to meet the specifications for high performance surfaces in demanding environments to ensure both the quality and safety of the endproduct over decades.
7.1.1.6 Conclusion on suitability and availability for Acidic surface treatments Architectural industry: To date, surfaces anodized with inorganic or organic acids cannot be seen as a 1:1 replacement for chromium trioxide-based coatings. Although standard corrosion requirements can generally be met, CAA was reported to be mainly applied when higher performance is mandatory. For these applications, the alternatives do not fulfil the more demanding requirements. Most importantly, no long term-term exposure data in real-world environments exist.
52 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
For conversion coatings based on tannic acid, standard corrosion requirements can generally be met, however the robustness of the process is still poor and the required paint adhesion cannot always be met with these products, especially once the process was scaled up to industrial applications. While the Qualicoat approval expired for the first tannic acid-based product, R&D is ongoing for modified formulations. At the current stage, the alternative is neither Qualicoat nor GSB approved for the architectural sector. Industrial upscaling and long-term corrosion tests will have to be performed before a final assessment on the performance can be made. At the current stage it is not known if tannic-acid-based systems will qualify as alternative to chromium trioxide. Automotive sector: It can be stated that anodizing treatments with inorganic or organic acids are technically not feasible as alternatives to chromium trioxide within the automotive sector. No completely chromium trioxide-free process chain is currently available, nor is implementation foreseen within the next decade, due to the complex supply chain. 7.1.2. Alternative 2: Cr(III)-based surface treatments
7.1.2.1 Substance ID and properties Cr(III) processes are generally based on the same principle as Cr(VI) processes. However, there are major differences in the distinct chemical composition of the solutions and required additives as well as the operating parameters and ancillary equipment, such as ion exchangers, depending on the kind of surface treatment. In general, predominantly two types of Cr(III) solutions are used: sulphate- and chloride-based. An overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.2.
7.1.2.2 Technical feasibility Table 12 summarizes the chromium trioxide-based surface treatment processes where Cr(III)-based surface treatments were assessed to be an applicable alternative.
Table 12: Sector specific overview on chromium trioxide-based surface treatments processes where Cr(III)-based technics are evaluated
Industry sector Surface treatment Substrate / coating
Chromate conversion Aluminium and aluminium alloys, Cd, Zn, ZnNi Architectural coating deposits Passivation, sealing, Automotive Aluminium and aluminium alloys, chromate conversion coating Chromate conversion Aluminium and aluminium alloys, copper, galvanised coating steel General engineering Grain oriented steel Steel insulation
7.1.2.2.1 Architectural industry General assessment: The difficulty in the use of alternative products arises when scaling up successfully tested chemicals from the laboratory to practical application in industrial facilities, to ensure the suitability of the final products in corrosive environments. After several years of development work, Cr(III)-based products still require further approval and testing to finally assess if they are equivalent to chromium trioxide. Some of these products are already approved by Qualicoat
53 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
and/or GSB. It was stated during the consultation that the performance of these alternatives may be equal for many applications to chromium trioxide-containing treatments for up to several years. In some countries (e.g. Spain) the majority of architectural applications have been done on a chromate- free-basis for the last 10 years. However, manufacturers in the building sector give warranty for chromium trioxide-based treatments for up to 30 years. Some of the tested coatings are colourless. Generally, chromium trioxide-based-coatings are visible which is preferred to ensure that a visual inspection of the effectiveness of the process can easily be made. It was stated that this is not an issue however, since several other methods exist to inspect the effectiveness of the coatings. Corrosion resistance: Initial corrosion testing of painted Al panels in acetic acid salt spray tests according to ISO 9227 showed inferior performance of tested Cr(III) systems compared to chromium trioxide-based conversion coatings. After 1000 h, significant paint blistering occurred, which is not in line with the specifications that require blistering grade 0 (S0). For sufficient corrosion resistance, high coating weights (50 - 200 mg/m²) are needed which again reduce the coating’s adhesion performance. Other Cr(III)-based products were tested for use within the building sector. It was reported that they met the main specifications (Qualicoat (sea-side level) or GSB (EL 631, 8.3.3.)) after painting on many substrates, such as steel, Zn, HDG, EG. The following tests were carried out for these products: corrosion protection, paint adhesion, coating weight, paint adhesion after boiling test, bending test, impact test. Adhesion: Adhesion performance in accordance with ISO 2409 was stated to be sufficient, while other companies reported problems with the paint adhesion performance. Some test programs were successful, whilst others failed. Reproducibility of Cr(III)-based processes was reported to be an issue not only in the architecture sector. Robustness: Various companies using Qualicoat approved alternative treatments experienced problems regarding poor paint adhesion or higher susceptibility to corrosion. In general, the Cr(III)- bath processes need to be monitored more carefully than chromium trioxide-based processes. Indeed, the alternative processes were stated to be more sensitive than chromium trioxide baths. Not only is the working window smaller, but also bath maintenance has to be performed in shorter intervals. As these kinds of coatings are generally thinner than with the conventional chromium trioxide-based processes, chromate-free coatings might be more susceptible to surface damage. In this regard, Qualicoat increased the requirements for architectural applications (also for chromium trioxide- containing treatments), to ensure a more robust quality control, especially for the newer applications, to reduce failures induced by wrong processing. Long-term experience: In addition to stringent mechanical adhesion tests and acidic salt spray testing for 1000 h, the Qualicoat and GSB approval both include a real-life test under harsh environmental conditions (sea-side conditions). Here, alternatives have to withstand outside marine environments in long term corrosion testing series that will take up to 10 years. Recently, filiform corrosion results were obtained for Al panels after 10 years exposure in sea-side conditions. It was shown that the panels passed the requirements of GSB. However, companies clearly cannot always rely on these accelerated test data from laboratory or first outdoor testing to substantiate the performance of a specific alternative product, as this was shown to result in many costly field failures over the last few years. Indeed, the alternatives are developed and adjusted continually, but the experience with the alternatives unadjusted in chemical composition and/or in process circumstances, are a maximum of 10 years. In the end, these data do not necessarily correlate to the ultimate performance of the coated surface over decades in a highly demanding seacoast environment or in proximity to industrial sites such as power stations, oil refineries or chemical plants as reported in chapter 5.1. Experience showed that companies withdrew from alternative treatments and went back to chromium trioxide-based
54 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES conversion coatings, since real life performance was clearly not satisfactory. Chromium trioxide- based coatings are a very tolerant system, while the alternatives are much more sensitive. Conclusion: To date, Cr(III)-based products are not a 1:1 replacement for chromium trioxide-based treatments. The reproducibility of the process is still poor, corrosion requirements and paint adhesion cannot always be met with Cr(III) processes. Most importantly, current products, although approved by Qualicoat or GSB, do not show sufficient corrosion protection when tested in real-life conditions.
Corrosion resistance Adhesion Reproducibility Long-term experience
Depending on substrate
7.1.2.2.2 Automotive General assessment: It was stated during the consultation that extensive R&D is ongoing on Cr(III)- based conversion coatings. Several industry sectors clearly confirmed that the reproducibility of the Cr(III)-based process is still poor. Some test programs were successful, while others failed. Due to the non-visibility of the coating (colourless), adequate process control may be more demanding. However, it was stated that this is not an issue, since several other methods exist to inspect the effectiveness of the coatings. Finding the right process window for good reproducibility remains very challenging, thus these coatings currently remain at low maturity. Corrosion resistance: Especially for high copper containing aluminium alloys, the corrosion resistance was reported to be clearly inferior compared to chromium trioxide-based conversion coatings. When applied on automotive specific Al alloys (AlMg), the corrosion performance is sufficient in laboratory scale (>240 h, NSS ISO 9227). Adhesion: The automotive sector confirmed that the adhesion properties of Cr(III)-based coatings are suitable for their applications. Conclusion: To date, Cr(III)-based products are not a 1:1 replacement for chromium trioxide-based conversion coatings. In laboratory scale, corrosion requirements can be met with Cr(III), while the reproducibility of the process is still poor. The maturity of this replacement technology is currently low. In summary, Cr(III) coatings as alternative to chromium trioxide are not yet technically feasible for the automotive sector.
Corrosion resistance Adhesion Reproducibility
for copper containing Al parts
clearly inferior”
7.1.2.2.3 General engineering Grain oriented steel insulation General assessment: Cr(III)-based alternatives were thoroughly investigated within the steel industry as replacement for chromium trioxide-based grain oriented steel insulation. The exact composition of this alternative is confidential business information. According to information from the sector, this alternative technique is currently not in line with their specifications, since results on key parameters were not satisfactory. Therefore, industrial trials on Cr(III)-based processes were stopped and the industry is focusing on an oxide-based alternative, that is described in chapter 7.1.9.
55 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Coating tension: As a key performance parameter, the coating tension does not meet the requirements from this industry sector. The tension imparted to the steel by this kind of coating is clearly less than the one generated by chromium trioxide coatings and impairs its magnetic properties. Magnetic properties: The reduced tension when using Cr(III) leads to poor magnetic properties (core losses). Core losses are the most important parameter for this process. The steel sold to customers must have guaranteed magnetic properties in compliance with international standards (IEC 60 404, Epstein frame and single sheet tester). Layer thickness: In this context, the layer thickness of Cr(III)-based coatings, which has a direct impact on the coating tension, has to be increased to reach the same imparted tension as with chromium trioxide coatings. (Thermo) optical properties: An increased thickness is not only detrimental for the (thermo) optical properties of the product which are no longer in line with customer demands, but also for increased dust generation during slitting operation, risk for burr generation and stacking factor (ratio between steel and coating which has to comply with IEC 60 404 standard). Additional critical parameters, which show satisfactory performance, are described as follows. Electric insulation properties are in line with the demands from industry. Laminations of electrical steel are stacked to form the iron core of electric transformators. The electric insulation is provided mainly by the final coating. Heat resistance does meet the requirements as long as phosphate-based coatings are used. Furthermore, the machinability of Cr(III)-based processes is sufficient. GOES is slit either by manufacturers or by customers. The insulation coating must not generate too much dust (this can be achieved e.g. by increasing layer thickness as mentioned above). Burr height is also a concern for transformator producers. If the hardness of the coating is too high, deburring will be cost- , time-, and material-consuming taking also the wear of the cutting tools into account. From an environmental point of view, use of Cr(III)-based coatings may generate NOx emissions on the coating line. Some national regulations (e.g. France) do not allow emission of NOx into the atmosphere. Furthermore, EU Directive 2008/50 Framework Air Quality Directive contains threshold limits for NOx. Here, an emissions capture system would have to be implemented which would be very expensive. As mentioned above, due to the current technical limitations, unsatisfactory test results in the past, and the quality restrictions identified during the trials, industry stated that Cr(III)-based coatings are not the preferred alternative. To date, industry is working on other oxide-based coatings as alternative to grain oriented steel insulation.
(Thermo) Coating Magnetic Layer Heat Electric NOx Machinability optical tension properties thickness resistance insulation emission properties
Chemical conversion coating General assessment: It was reported that for sufficient corrosion protection on steel, high coating weights are needed which in turn reduce adhesion properties. Cr(III)-based treatments as alternative to conversion coatings on steel (HDG / CRS) are currently of low maturity in this sector. They are also under investigation as an alternative to chromium trioxide-based conversion coating on metallic chromium. This is an intermediate step, as afterwards a final coating layer will be applied.
56 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Corrosion resistance: When tested on Zn-coated steel and steel surfaces, the corrosion performance is sufficient. For galvanised steel sheets, white rust appearance issues were experienced when the fresh material is exposed to severe environmental conditions during logistical chains. Adhesion to subsequent layer: When applying Cr(III)-based conversion coatings on metallic chromium, adhesion properties for the final coating layer look promising in first experiments in the laboratory scale. Wear resistance: When Cr(III)-based treatments were applied on metallic chromium in initial laboratory testing, the required wear resistance of the final coating seems feasible. Reproducibility: Companies from several industry sectors confirmed that the reproducibility of the process is poor. Due to the non-visibility of the coating (colourless), it is also more demanding to control the coating properly. Conclusion: To date, Cr(III)-based products cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings. On some steels, corrosion performance is sufficient but the robustness of the process clearly needs to be improved. When applied on metallic chromium, development is at low maturity, though first laboratory test showed promising results. In summary, Cr(III)-based products are not seen as an appropriate alternative to chromium trioxide-based treatments.
Corrosion resistance Adhesion Wear resistance Reproducibility
On some steel substrates On metallic chromium On metallic chromium
7.1.2.3 Economic feasibility Against the background of significant technical failure of these alternate systems, no detailed analysis of economic feasibility was conducted. First indications were made, stating that the process is in general economically feasible. General engineering: For grain oriented steel insulation, implementation of capture systems for NOx emissions would be necessary and cost intensive.
7.1.2.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. As worst case scenario, chromium (III) chloride is classified as Skin Irrit. 2, Eye Irrit. 2, Acute Tox. (Acute Toxicity). As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances.
7.1.2.5 Availability Architectural sector: Alternative products are available for this sector and partly approved by Qualicoat and/or GSB. Extensive research is ongoing within the industry, especially for the assessment of the long-term performance of the alternative coatings. The Qualicoat approval is often granted as preliminary approval while real-life, long-term testing is outstanding. Nevertheless, manufacturers in the building sector generally have to give a 25 year warranty for their products, although at the current stage, Cr(III)-based alternatives have not been tested for such a long lifetime. The Qualicoat approval as such is granted on test panels which are coated under clean lab conditions in the absence of interferences and so do not reflect industrial production conditions. From current
57 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
experience it cannot be confirmed that the available and approved alternative treatments are in line with the long-term performance criteria of the architectural sector. As such, another 10 years are necessary to finally assess the performance in a harsh outdoor environment. Automotive sector: CCC is still performed with chromium trioxide. For the global automotive market, the products and especially exterior parts have to meet the specifications for high performance surfaces in demanding environments to ensure quality and safety of the endproduct over decades. Current R&D on Cr(III) conversion coatings is at low maturity. Therefore, at least 10 years are necessary to fully develop and implement these alternatives. General engineering: Extensive R&D has been ongoing for several years already for the evaluation of potential alternatives to grain oriented steel insulation. So far, industry identified two potential replacement techniques for this purpose, which are other oxide-based coatings and Cr(III)-based coatings. For the time being, research focuses on other oxide-based coatings, since previous work on Cr(III)-based coatings revealed unsatisfactory performance results especially with regard to coating tension. In case current work on other oxide-based coatings would not be successful, industry would have to restart R&D on Cr(III) in order to try to adjust the formulation and/or the coating conditions to meet the so far not fulfilled parameters that were identified during the first industrial development phase of Cr(III)-based coating. This R&D phase would start when other oxide-based coatings development definitely fails and will take minimum 5 years. For optimization work on Cr(III), at least two years are foreseen. Therefore, a minimum of an additional 7 years would be necessary for the development of an alternative, if no major drawbacks occur. For CCC alternatives on metallic chromium, R&D is ongoing, former replacement developments concentrated on a series of pre-treatment steps followed by a primer before applying the final coatings. Although the adhesion of the lacquer seemed suitable, the wear resistance was clearly not in line with the requirements. In addition, for one of the applied pre-treatment steps, safety concerns were raised. Therefore, this treatment was not developed any longer, so that recently tests on a completely new Cr(III) alternative were started. In terms of a sustainable research process, search for replacements includes also an alternative for the chromium trioxide-based metallic chromium layer in combination with alternatives to the conversion coating and an appropriate final coating layer. Consequently, R&D is currently in a very early stage and development until product readiness will take at least additional 10-15 years.
7.1.2.6 Conclusion on suitability and availability for Cr(III)-based processes Architectural sector: For this use, Cr(III)-based treatments are partly in line with standard specifications from Qualicoat or GSB, but their long-term performance can currently not be finally assessed. From customers’ outdoor experience, performance is clearly inferior compared to chromium trioxide, especially in a marine environment. Automotive sector: It can be stated that Cr(III)-based surface treatments are no technically feasible alternative to the aforementioned chromium trioxide-based processes within the automotive sector yet. Although corrosion requirements can be met in the laboratory, the major technical limitation is the poor reproducibility of Cr(III)-based solutions. Since the process needs to be controlled very carefully and is highly sensitive to impurities, it is currently of low maturity. General engineering: Due to the current technical limitations and unsatisfactory test results in the past, industry stated that Cr(III)-based coating is not the preferred alternative regarding the quality restrictions identified during the trials. Taking uncertainties or successful industrial upscaling of an alternative into account, at least 7-10 years would be necessary to fully implement a replacement technique and to ensure the quality needs of the highly demanding customers worldwide.
58 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
To date, Cr(III) coatings cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings for this sector. The major technical limitation is the poor reproducibility of Cr(III)-based solutions. Since the process needs to be controlled very carefully and is highly sensitive to impurities, it is currently of low maturity. It is not known if Cr(III) will qualify as alternative in this industry sector, as other alternatives are more promising In summary, to date Cr(III) is not an alternative to the current systems in the architectural, automotive and general engineering sector. Therefore, at least 10 years are necessary to fully implement a replacement technique.
7.1.3. ALTERNATIVE 3: Silane/Siloxane and sol-gel coatings
7.1.3.1 Substance ID and properties Sol-gel describes a wide variety of processes. In general, the evaporation of the solvent and the subsequent destabilization of the sols lead to a gelation process and the formation of a transparent film due to the small particle size in the sols. Currently, sol gel technology is expanding rapidly, extensive R&D effort is being made and many new products are appearing on the market, especially since the advent of hybrid and nanocomposite materials. The following description of the sol-gel process is derived from Wang & Bierwagen (2009). By using sol-gel coating processes, a network of oxides is formed on the substrate created by the progressive condensation reactions of molecular precursors in a liquid medium. In general, two main processes -an inorganic and an organic one - can be distinguished. When using the inorganic sol-gel process, a network is formed by a colloidal suspension (usually oxides) and the gelation of the sol (colloidal suspension of very small particles, 1 to 100 nm). The organic approach is the most widely used sol-gel process and generally starts with a solution of monomeric metal or metalloid alkoxide precursors in an alcohol or other low-molecular weight organic solvent (M(OR)n). M is a network-forming metal of transition metal such as Si, Ti, Zr, Al, Fe, B, etc. and R is typically an alkyl group (CnH2n+1). Typical precursors are silanes and siloxanes (=silicones). An overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.3. Depending on the geometry (size and shape) of the part to be coated, different technologies such as spraying, immersion, electrodeposion or dip-spin coating can be used for applying a sol-gel coating. The most common and commercially used application technique for sol-gel coatings is dip-spin technology, while spraying technology is the most commoly used technique within the aerospace sector. The dip spin application is performed in a spray chamber using a mesh basket. The parts to be coated with a sol-gel coating via dip spin technology are placed on a conveyor and then metered by weight into a wire mesh basket with a diameter generally between 0.5 to 1.0 m. The basket (full of parts) is then submerged into a coating vat. The basket is then raised out of the coating solution, yet still remains in the vat, and spun up to 600 rpm (revolutions per minute). A drying period, resulting in the formation of the respective sol-gel coating, is necessary after the coating application. The exact drying technique varies dependent on different microstructures, quality requirements, and practical applications.
59 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.3.2 Technical feasibility Table 13, summarizes the chromium trioxide-based surface treatment processes where silane or siloxane (mostly applied as sol-gel coatings) and other Sol-Gel coatings are considered to be an alternative.
Table 13: Chromium trioxide-based surface treatments processes where sol-gel coatings may be an alternative
Industry sector Surface treatment Substrate / coating
Architectural Chromate conversion coating Aluminium and aluminium alloys
Sealing after anodizing, Automotive Aluminium and aluminium alloys Chromate conversion coating
General assessment: From academic research it was stated that thin films without the need for machining or melting can be applied. Literature also highlights that complex shapes can be coated with the sol-gel coating process as (Wang et al, 2009). Current challenges with this process include: - Interface properties of sol-gel coatings (adhesion, delamination) determine the quality of the sol-gel coating. General approaches or methods to evaluate these properties have not yet been established; - Processing times are very long as the curing process is performed at high temperatures; and - Due to a substantial volume contraction and internal stress accumulation caused by the large amount of evaporation of solvents and water, the coating can easily establish cracks and therefore, the formation conditions of the sol-gel coatings have to be carefully controlled during the drying process (Wang & Bierwagen, 2009).
These scientific statements and expectations from Wang and Coworkers (2009) are in contrast to numerous industry experience with sol-gel coatings.
7.1.3.2.1 Architectural industry General assessment: First alternative products based on Sol-Gel technology were developed for the treatment of aluminium before painting for architectural purposes. In addition to coatings currently in development, one Zr-based Sol-Gel product is already approved as pre-treatment by Qualicoat and/or GSB, only when applied with an approved powder coating system. According to the manufacturer, the product can be used on steel, aluminium and zinc coated surfaces. Corrosion resistance: As mentioned, when applied with an approved powder coating system, this product meets the standard requirements of Qualicoat and GSB (1000 h ISO 9227). However, these newly developed systems combine a pre-treatment (CCC) with a final coating (lacquer). The conversion coating alone does not fulfil the specifications of the architectural sector. To date, no “universal” alternative system combining CCC and lacquer does exist, and so decisions have to be made on a case by case basis, depending on the specific applications. Importantly, the protective properties are derived from both the treatment and lacquer. The crucial requirement for conversion coating is the good adhesion of the subsequent layer to ensure long-term-performance of the coating system. Coating of complex parts: In general, the Sol-Gel technology showed limitations in application of the coating to complex parts. New strategies have to be developed, which is the main objective of an ongoing project within the architectural sector. In this project, an electrophoresis process is being assessed and developed to apply the anti-corrosion coatings through sol-gel technique for complex geometry parts.
60 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Reproducibility: Several companies from different industry sectors indicated that the process for the industrial application of sol-gel coatings is complex and of limited reproducibility. Adhesion: According to Qualicoat approval, the Zr-based product meets the required classification of GT0 according to ISO 2409. For other products in the development process, total loss of adhesion was observed. Long-term experience: In addition to stringent mechanical adhesion tests and acidic salt spray testing for 1000 h, the Qualicoat and GSB approvals both include a real-life test under harsh environmental conditions (sea-side conditions). Here, alternatives have to withstand outside marine environments in long term corrosion testing series that will take up to 10 years. Indeed, the alternatives are developed and adjusted continually, but the experience with the alternatives unadjusted in chemical composition and/or in process circumstances are a maximum of 10 years. In the end, these data do not necessarily correlate to the ultimate performance of the coated surface over decades in a highly demanding seacoast environment or in proximity to industrial sites such as power stations, oil refineries or chemical plants. Chromium trioxide-based coatings are a very tolerant system, while the alternatives are much more sensitive Conclusion: To date, Sol-Gel-based products cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings but are promising alternatives. Although standard corrosion requirements can generally be met, major drawbacks are the limited process reproducibility and the problems in applying the coatings to complex geometries. Most importantly, for current products, although approved by Qualicoat or GSB, no long term-term exposure data in real-world environments exist.
Long-term Corrosion resistance Adhesion Reproducibility Complex parts experience
7.1.3.2.2 Automotive sector
Sealing after anodizing, chromate conversion coating General assessment: Within the automotive sector, silane-based alternatives such as Sol-Gel technology are intended to be used as alternative to sealing after anodizing and chromate conversion coating. Corrosion resistance: For fulfilling the requirements of the automotive sector, treated surfaces have to withstand corrosion for a certain timeframe. Depending on the process, different requirements exist. When Sol-Gel technology is applied on anodized aluminium of high purity, the sealed surface does meet the corrosion requirements (>24 h CASS, ISO 9227). In another test series, silane/siloxane compounds were applied on Zinc coating for passivation and zinc-based materials as alternative to chromate conversion coating. Again, the results were in line with the specifications from the automotive industry (passivation >240 h NSS, ISO 9227; CCC >96 h NSS, ISO 9227). The issue of this alternative though is the still poor reproducibility of the current technology. Chemical resistance: Chemical resistance of surfaces sealed with Sol-Gel coatings was tested. Resistance against acids (10 min immersion at pH 1) and alkaline (10 minutes immersion at pH 13.2) was found to be sufficient. Reproducibility: It was indicated that the process for the industrial application of Sol-Gel coatings may be complex and of limited reproducibility.
61 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Coating of complex parts: In addition, technologies showed limitations in applying the coating to complex parts and so more sophisticated strategies must be developed to overcome this issue. Work on these challenges is currently ongoing and research is mainly being conducted at a laboratory scale. Process temperature: Several products were already tested by the industry and found to be not sufficient since the curing temperatures are above 100°C, which might not be applicable for all preparations. Conclusion: Sol-Gel coatings at the current stage are a promising alternative but technically not feasible due to poor reproducibility and low maturity. Further R&D is necessary to improve their performance, a TRL is not defined yet.
Corrosion Process Chemical resistance Reproducibility Complex geometry resistance temperature
7.1.3.3 Economic feasibility Against the background of significant technical failure of these alternate systems, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible.
7.1.3.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. In addition, publically available information on specific alternatives products was evaluated. However, please note that the exact substance identity and composition of products used in the Sol- Gel process is very often not known as this is confidential business information. Therefore, only the hazard classifications for the Sol-Gel matrix could be taken into account. In a worst case they are classified as Flam. Liq. (Flammable liquid) 3, Acute Tox. 4, Eye Dam. (Serious eye damage) 1, Skin Irrit. 2, Eye Irrit. 2, STOT SE (Specific target organ toxicity, single exposure) 3, Asp. Tox. (Aspiration hazard) 1, Muta. (Germ cell mutagenicity) 1B, Carc. (Carcinogenicity) 1B. The substance vinyl trimethoxysilane (VTMS) constitutes the worst case scenario and is included in the CoRAP (Community Rolling Action Plan), indicating substances for evaluation by the EU Member States in the next three years. The evaluation aims to clarify concerns that the manufacture and/or use of these substances could pose a risk to human health or the environment. As such, a transition from chromium trioxide – which is a non-threshold carcinogen – to one of the above mentioned alternative products could constitute a shift to less hazardous substances. However as at least one of the alternate substances is itself classified for mutagenicity and carcinogenicity, any replacements will need to be carefully evaluated on a case by case basis.
7.1.3.5 Availability Architectural sector: A first alternative product based on Sol-Gel technology was approved already in 2012 by Qualicoat and/or GSB, only when applied with an approved powder coating. R&D on further alternatives is ongoing, especially on the improvement of the process control. Importantly, for the assessment of long-term performance as required by Qualicoat, outdoor testing of Al panels has been initiated but has yet to last up to 10 years. However, as these tests are only carried out on panels and not complete buildings, results will not necessarily correlate to the ultimate performance of the final product.
62 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Automotive sector: Investigation of Sol-Gel replacement technology is ongoing at laboratory scale. If these tests are successful, extensive outdoor testing will have to be carried out to assess the quality and functionality of the new developments in real-life conditions. However, for final analysis before implementation, long-term field experience is mandatory. For the global automotive market, the products and especially exterior parts have to meet the specifications for high performance surfaces in demanding environments to ensure the quality and safety of the endproduct over decades. The research on these challenges is currently ongoing in various industry sectors. Therefore, Sol-Gel clearly is a long term solution since qualification and implementation into the supply chain will take 10-15 years.
7.1.3.6 Conclusion on suitability and availability for Silane or siloxane-based sol-gel processes For architectural and automotive applications, corrosion requirements can be met under laboratory conditions, while the major technical limitation is the poor reproducibility and the inability to coat parts with complex geometries. Most importantly, for a current product that is approved by Qualicoat or GSB for architectural applications, no long term-term exposure data in real-world environments currently exists. In summary, chromium trioxide-free Sol-Gel systems are from a technical point of view clearly not equivalent to chromium trioxide-based surface treatments and are currently not a general alternative. Since these systems are in early research stages, another 12-15 years might be necessary to develop and implement these systems into real life, if no major drawbacks occur along the way.
CATEGORY 2 ALTERNATIVES The alternatives assessed in this section are mainly discussed in literature and were mentioned only few times during the consultation phase. In most cases, they are in very early research stages and showed clear technical limitations when it comes to the demanding requirements from the different sectors. However, they currently may only be suitable for specific industry sectors or for niche applications but not as general alternatives to Cr(VI) containing coating systems.
7.1.4. ALTERNATIVE 4: Manganese-based processes
7.1.4.1 Substance ID and properties This alternative comprises all manganese containing processes such as permanganate conversion coatings, permanganate / phosphate conversion coatings and manganese-based sealing processes. In all processes, the permanganate is applied by immersing the substrate in the respective solution.
- The permanganate anion MnO4 is a strong oxidising agent which is reduced to manganese (IV) oxide, while elementary metal is oxidised and dissolved from the substrate as cation (Lee et al, 2013). Adding other substances such as phosphate to the conversion solution can enhance the corrosion resistance of the conversion coating (Lee et al, 2002). For use in sealing applications, a manganese salt solution was tested. The pores of the anodic coating are filled with manganese oxide (MnO2) and the manganese oxide deposit grows from the pore base. Deposition is continued until it reaches the outer surface of the coating (Alwitt & Liu, 2001). A non-exhaustive overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.4.
63 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.4.2 Technical feasibility Manganese-based processes are assessed as an alternative for the following chromium trioxide-based surface treatments (Table 14):
Table 14: Chromium trioxide-based surface treatments processes where manganese-based products may be an alternative
Industry sector Surface treatment Substrate / coating
Chromate conversion Aluminium and aluminium alloys, Cd, Zn, ZnNi Architectural coating deposits
7.1.4.2.1 Architectural industry General assessment: Manganese-based pre-treatments are rarely used in the architectural industry, they cannot be seen as a general alternative since more promising substances exist. Corrosion resistance: It was reported that the corrosion performance of aluminium substrates treated with permanganate conversion coatings can be in accordance with the standard Qualicoat requirements if treated products are subsequently painted. Specifications ask for 1000 h in acidic salt spray test according to ISO 9227. Adhesion of paint: The adhesion characteristics are not sufficient, products do not pass cross-cut test. The required classification of GT0 after 168 h hot water immersion according to ISO 2409 is not reached. Conclusion: To date, permanganate conversion coatings are clearly not a 1:1 replacement for chromium trioxide-based conversion coatings. Although standard corrosion requirements may be met for some applications if products are painted, the adhesion properties are not sufficient. Currently, no approved product is available. Furthermore, no long term-term exposure data in real-world environments exist.
Corrosion resistance Adhesion Long-term experience
Only sufficient if painted
7.1.4.3 Economic feasibility Against the background of significant technical failure of these alternative systems, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible.
7.1.4.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. As worst case assumption, Potassium permanganate is classified as Ox. Sol. (Oxidising solid) 2, Acute Tox. 4, Aquatic Acute 1, Aquatic Chronic 1, Skin Corr. 1C. As such, transition from Chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances.
64 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.4.5 Availability Architectural industry: Current development products do not fulfil the requirements of the building sector. So far, no product has been granted Qualicoat or GSB approval. The final success of permanganate-based alternatives cannot be foreseen at the moment. Following the technical assessment, the relevance of these systems is questionable.
7.1.4.6 Conclusion on suitability and availability for manganese-based processes In literature, few development products as replacement systems to chromate conversion coating have been reported so far. Thus, it can be concluded that conversion coatings techniques based on permanganate compounds are technically not yet equivalent to chromium trioxide-based processes and are therefore not a general alternative for architectural applications. According to their performance and the current, very early stage of research, it is questionable if these systems will develop into suitable alternatives.
7.1.5. ALTERNATIVE 5: Molybdates and Molybdenum-based processes
7.1.5.1 Substance ID and properties The coating industry uses molybdate for various processes. It has been used as corrosion inhibitor (e.g. zinc molybdate, calcium zinc molybdate) since the early 1970s and is also used as a molybdenum-based metal coating. Here, a molybdenum coating can be applied by immersion, creating a molybdate-based conversion Coating (MoCC) to form a protective oxide layer on the surface of the metal to be treated, which provides corrosion resistance. Two main types of MoCC are possible: a coating based on sodium molybdate (Na2MoO4•2H2O), and a coating based on a mixture of molybdate and phosphate (e.g. as phosphoric acid). Stabilizer additives such as cerium fluoride are used for the MoCC. A non-exhaustive overview on general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.5.
7.1.5.2 Technical feasibility Table 15 summarizes the chromium trioxide-based surface treatment where molybdate-based processes were assessed as a potential alternative.
Table 15: Chromium trioxide-based surface treatments where molybdate-based processes may be an alternative
Industry sector Surface treatment Substrate / coating Aluminium and aluminium alloys, Zn-coated Architectural industry Chromate conversion coating steel
7.1.5.2.1 Architectural industry Corrosion resistance: Salt spray testing of painted panels suggested that the corrosion resistance of MoCC is inferior to chromate conversion coating and does not meet the requirements. When tested according to ASTM B-117, loss of adhesion occurred significantly earlier compared to panels with chromium trioxide-based treatment. Molybdates may be used as additives to organometallic coatings. Adhesion: Several companies stated that paint adhesion was often not in line with the Qualicoat requirements. While some test series were successful, other failed to meet the specifications according to ISO 2409.
65 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Chemical resistance: Resistance against several chemicals does not fulfil the requirements of the building sector. Robustness: As stated above, adhesion properties cannot be controlled adequately since molybdate conversion coatings lack robustness, if the process is not stringently controlled. The MoCC process has to be carefully controlled, as the final corrosion resistance from the treated surface is highly dependent on the substrate, its pre-treatment and the process conditions. Other industry sectors terminated development of this technique since it was too difficult to control deposition of MoCC. Long-term experience: Currently, none of the products tested is approved by Qualicoat or GSB. Therefore, no long-term exposure data in real-world environments exists. Manufacturers in the building sector generally have to give a >25 years warranty for their products, although at the current stage, the chromate-free alternatives have not been tested for such a long lifetime. The Qualicoat approval as such is granted on test panels which are coated under clean lab conditions in the absence of interferences and so do not reflect industrial production conditions. Conclusion: MoCC is clearly not a 1:1 replacement for chromium trioxide-based conversion coatings. Standard corrosion performance is inferior to chromium trioxide, the robustness of the process is still poor and paint adhesion cannot always be met.
Corrosion Long-term Adhesion Robustness Chemical resistance resistance experience
7.1.5.3 Economic feasibility Against the background of significant technical failure of these alternate systems, no detailed analysis of economic feasibility was conducted. First information was provided that chemical cost can be higher by a factor 2. However, based on the literature research and consultations there is no indication that the discussed alternative is not economically feasible.
7.1.5.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Sodium molybdate is classified as Skin Irrit. 2, Eye Irrit. 2, Acute Tox. 4, STOT SE 3. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances.
7.1.5.5 Availability According to literature research, some R&D has been performed in the last years on molybdenum conversion coating. For architectural applications no molybdate-based product is currently approved by the quality labels Qualicoat or GSB. None of the systems currently fulfils the requirements of the aviation sector or the architectural industry. During the consultation, no information on ongoing R&D efforts within these sectors was provided. It was reported that these systems failed already at the screening phase. Following the technical assessment, the relevance of these systems is questionable. The final success of molybdenum-based alternatives cannot be determined at the moment. During the consultation, companies reported that these systems have already been screened out at an early stage, as more promising alternatives were chosen for further development.
66 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.5.6 Conclusion on suitability and availability for molybdates and molybdenum-based processes Few development products have been reported as replacement systems to chromate conversion coating so far. All of them failed to meet the requirements of the architectural industry already at laboratory scale. During the consultation, companies reported that these systems have already been screened out an early stage, as more promising alternatives were chosen for further development. It can be concluded that conversion coatings based on molybdate compounds are technically not equivalent to chromium trioxide-based products and are therefore not a general alternative for architectural applications on aluminium substrates. Following the technical assessment, the relevance of these systems is questionable.
7.1.6. ALTERNATIVE 6: Organometallics (Zr- and Ti-based products)
7.1.6.1 Substance ID and properties Since the late 1970s, organometallic coatings based upon organo-titanates, organo-zirconates or organo-zircoaluminates have been reported and found some applications in adhesive technology. It is generally considered that they form interfacial primary bonds to the substrate via reaction with surface protons. So far, titanates have not found wide use in adhesive technology but are used in the manufacture of some film laminates. In the last few years, a new generation of environment-friendly conversion coatings based on titanium or zirconium oxides has attracted extensive attention owing to good corrosion and wear resistance. Moreover, the new conversion coatings can operate at lower process temperatures. These Ti/Zr-based conversion coatings have been mostly used on aluminium and magnesium alloys. Reports applying to zinc have been scarce until now (Guan et al, 2011). Products based on fluorotitanic and fluorozirconic acid were stated as alternatives for conversion coatings in the architectural sector. A patent protected Cr(VI)-free passivation treatment was developed specifically for aluminium alloys. This commercially available solution is based on hexafluorozirconate and is qualified under the United States Military Standard MIL-DTL-81706 Class 3 for military purposes. The coating can be used as a final finish and can also serve as a base for paints, high performance topcoats, powder paints, lacquers, or as a base for rubber bonding. A non-exhaustive overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.6.
7.1.6.2 Technical feasibility Zirconium and titanium-based products are assessed as an alternative for the following chromium trioxide-based surface treatments (Table 16):
Table 16: Chromium trioxide-based surface treatments where fluorotitanic and fluorozirconic-based products may be an alternative
Industry sector Surface treatment Substrate / coating
Chromate conversion Architectural sector Aluminium and aluminium alloys, Zinc-coated steel coating Chromate conversion General engineering Steel, HDG, cold rolled steel, CES, metallic chromium coatings
67 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.6.2.1 Architectural industry
Chromate conversion coating General assessment: Several alternative products based on fluorozirconic acid were developed for the treatment of aluminium before painting for architectural purposes. Some of these products are already approved by Qualicoat and/or GSB. It was stated during the consultation that the performance of these alternatives are for many applications equal to chromium trioxide-containing treatments for up to 15 years. In some countries (e.g. Spain) the majority of architectural applications have been conducted on a chromate-free-basis for the last 10 years. However, manufacturers in the building sector give warranty for chromium trioxide-based treatments for up to 30 years. These newly developed systems combine a pre-treatment (CCC) with a final coating (lacquer). The conversion coating alone does not fulfil the specifications from the architectural sector. When overcoated with a suitable non-chrome-lacquer, the requirements can be met. To date, no “universal” alternative system combining CCC and lacquer does exist though, and so decisions have to be made on a case by case basis, depending on the specific applications. Importantly, the protective properties are derived from both the treatment and lacquer. The crucial requirement for conversion coating therefore is the good adhesion of the subsequent layer to ensure long-term-performance of the coating system. Current lacquer systems are based on a polyurethane-matrix in which corrosion inhibitors on titanium- zirconium- or Cr(III)-base are incorporated. Furthermore, multicoating systems are under development with 2 lacquers on top of the conversion coating. For these systems, no data on long- term outdoor performance is currently available. Most of these coatings are colourless. Generally, chromium trioxide-based-coatings are visible which is preferred to ensure that a visual inspection of the effectiveness of the process can easily be made. However, it was stated that this is not an issue, since several other methods exist to inspect the effectiveness of the coatings. Corrosion resistance: It was reported during the consultation that the corrosion performance of painted aluminium substrates treated with these replacement products gets close to meeting or partly meet the 1000 h in acidic salt spray test according to ISO 9227, while for zinc coated steel surfaces the required 500 h was reached. It is of note that none of the alternate products outperforms chromium trioxide. Standard Qualicoat requirements can be fulfilled with these products. Some higher requirements for special applications (NSS, AASS 2000 h, < 2 mm) are clearly not reached with the alternative treatments. Adhesion: In laboratory tests, the required result of GT0 according to ISO 2409 is reached. More importantly, several companies stated that a considerable number of instances were observed where paint performance has been poor in practice and resulted in expensive remedial action being necessary. Robustness: Various consumers using Qualicoat approved alternative treatments experienced problems regarding poor paint adhesion or higher susceptibility to corrosion. In general, the alternate processes need to be monitored more carefully than chromium trioxide-based processes. Indeed, the alternative processes were stated to be more sensitive than chromium trioxide baths. Not only is the working window smaller, but also the bath maintenance has to be performed in shorter intervals. As these kinds of coatings are generally thinner than the conventional chromium trioxide-based processes, chromate-free coatings might be more susceptible to surface damage. In this regard, Qualicoat increased the requirements for architectural applications (also for chromium trioxide- containing treatments), to ensure a more robust quality control especially for the newer applications, in order to reduce failures induced by wrong processing. Process engineering: Alternatives are combinations of CCC and lacquers. The lacquers are on a polymer basis which have to be sprayed, compared to conventional chromium trioxide-based coil-
68 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES coatings that are applied in baths. For these applications, the coating lines have to be adapted and it has been found that complex geometries are difficult to coat. Application of the polymer-lacquers has to be controlled carefully as delamination can occur due to inhomogeneous drying. Long-term experience: As stated in chapter 5.1, the majority of the alternative systems are potentially robust enough to meet even the long-term requirements of the architectural sector and are already applied successfully in many circumstances. However, annual evaluations worldwide showed that in the last 5 years the statistics of failures in salt spray testing were always in favour of samples treated with Cr(VI) by 2 to 7%! The reason for this is still unclear. Furthermore, for special, more demanding environments it was recently reported that the widely used alternatives based on organometallics show an increased sensitivity to chloride salts: After 4-8 years, corrosion and adhesion failures were observed on buildings exposed to sea-side environments in the Netherlands. This is not consistent with the performance of these systems in Spain, where these failures were not observed. This effect may be correlated to the significantly more humid environment in the Netherlands, which, in combination with UV-radiation, leads to a much faster degradation of the lacquer system than in dry surroundings. Another limitation of these alternate systems is that they provide reduced protection with increasing amount of Cu/Fe in the Al alloys. Besides that, the aluminium industry is moving towards more recycling and the amount of alloying elements are changing. Therefore, several projects were initiated recently to deeper analyze these findings and to further develop the alternative systems taking these potential issues into account. Conclusion: Although standard corrosion requirements for Zr- and Ti-based alternatives can generally be met, in long term-term exposure several failures occurred. It can be stated that they may be suitable for the majority of architectural applications, while for special uses - not only in humid surroundings - further R&D is necessary.
Corrosion resistance Adhesion Robustness Long-term experience
Not sufficient in humid
environments
7.1.6.2.2 General engineering General assessment: Alternatives based on Zr- or Ti-coatings cannot be seen as a 1:1 replacement, but will need adjustment of the current production line and process conditions or a change to a different treatment in some cases. In contrast to acidic treatments containing chromium trioxide, the chromate-free pre-treatments cannot compensate for any inadequacies in the cleaning process. Corrosion resistance: It was reported during the consultation that the corrosion performance of selected steel substrates such as HDG and cold rolled steel treated with Zr- and Ti-based products get close to meet or only partly meet the requirements of industry when tested at the laboratory scale (>350 h without delamination, EN 13523-8). Layer thickness: In general, these alternatives require the application of thicker layers to achieve a corrosion resistance comparable to chromium trioxide-based coatings. Adhesion is severely compromised if the film is too thick and this can lead to in-service coating failures that are unrelated to corrosion sensitivity. In case of Zr/Ti-coatings, more detailed inspections are needed regarding layer thickness by width and length. The layer thickness must not exceed 1 µm (EN 13523-1), measured by an electrical probe placed on the coating which develops an electromagnetic field in the base metal. Adhesion: Several companies stated that the required result for adhesion (degree of delamination 0-1 (EN 13523-6, ISO 2409) is reached.
69 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Aesthetics: Optical properties also play a crucial role since customers in the highly competitive market are very sensitive to aesthetic aspects. When Zr- or Ti-based alternatives are used, colour change is only marginal. Robustness: The alternative treatments are more difficult to monitor in production compared to traditional chromium trioxide-based systems. This is particularly an issue where polymeric additions are made to the formulation to improve performance. It was confirmed during the consultation that this technology is currently not stable on zinc layers. Conclusion: To date, Zr- and Ti-based products cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings. Standard requirements can generally be met, the robustness of the process needs to be improved and the layer thickness has to be carefully inspected during the treatment.
Corrosion resistance Adhesion Aesthetics Robustness Layer thickness
7.1.6.3 Economic feasibility Against the background of significant technical failure of these alternate systems, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible. However, fluoric acids are very aggressive products in general and investment for modification of the surface treatment line may be needed. Also bath maintainability has to be evaluated.
7.1.6.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Classification and labelling information of substances and products reported during the consultation was reviewed. In addition, publically available information on specific alternative products was evaluated. However, the exact substance identity and composition of products used is very often not known as this is confidential business information of suppliers. As worst case assumption, fluorotitanic acid is classified as Met. Corr. 1, Acute Tox. 2, Skin Corr. 1B, Eye Dam. 1. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances.
7.1.6.5 Availability Architectural sector: Several Zr- and Ti-based products exist on the market and are approved by Qualicoat and/or GSB. R&D on further alternatives is ongoing, especially for the improvement of the process control. In autumn 2014, further products based on fluorozirconic acid plus polymer are subject to submission for Qualicoat and GSB approval. It is estimated that the approval process will take at least 5 years. Importantly, during these 5 years only preliminary approval can be obtained, since the time will not be sufficient to get a clear answer on the long-term performance of this product. For this assessment, outdoor testing of Al panels was initiated as required by Qualicoat. This testing will last for up to 10 years. For some products, these tests have already been passed successfully. However, as these tests are only carried out on panels and not complete buildings, results will not necessarily correlate to the ultimate performance of this product when used on an industrial scale.
70 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
General engineering: Several products based on these substances are already commercially available. In the coil-coating industry, there has been some utilisation of Ti/Zr-base coating processes. However, R&D efforts are still ongoing to improve the robustness of the alternative process.
7.1.6.6 Conclusion on suitability and availability for fluorotitanic- and fluorozirconic-based products Architectural sector: It can be stated that the Zr- and Ti-based alternatives may be suitable for the majority of architectural applications, while for special uses - not only in humid surroundings – further R&D is necessary, as these systems do not provide the required long term performance. Experience showed that failures arose from industrial use of replacement products within the last few years. Therefore, doubts still remain on the ultimate performance of these alternate conversion coatings. Currently, Zr- and Ti-based products cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings. If today a solution is stated to be applicable, another 5-10 years are necessary to finally decide on its long term performance. General engineering: Some replacement systems to CCC have been tested so far by the steel processing industry. Although the Zr/Ti-based technique is already in use in some production lines, doubt still remains on the overall performance of these replacement coatings. To date, Zr- and Ti- based products cannot be seen as a 1:1 replacement for chromium trioxide-based conversion coatings for this sector. For successful industrial upscaling of an alternative, at least 10 years are necessary, if no major drawbacks occur.
7.1.7. ALTERNATIVE 7: Benzotriazole-based processes, e.g. 5-methyl-1H-benzotriazol
7.1.7.1 Substance ID and Properties 5-Methyl-1H-benzotriazol was tested as potential alternative for chromium trioxide in passivation of copper. Passivation of copper using chromium trioxide is a main step within production of specialized screens. Benzotriazoles, e.g. 5-methyl-1H-benzotriazol are corrosion inhibiting substances commonly used in primers providing copper blocking properties. 5-methyl-1H-benzotriazol forms a complex with copper metal at its surface, leading to stabilization of copper and inhibiting oxidation as long as the layer stays intact. An overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.7.
7.1.7.2 Technical feasibility 5-Methyl-1H-benzotriazol was tested as potential alternative for chromium trioxide in passivation (post-treatment conversion coating) of copper, referred to as conversion coating of copper in the following paragraphs.
Industry sector Surface treatment Substrate / coating
General engineering Chromate conversion coating copper
General assessment: When using chromium trioxide, the unique properties of the substance enables processing pickling and chemical conversion of copper within one single step. So far, it is not possible to replace chromium trioxide with one substance achieving both goals. Therefore pickling and passivation treatments need to be separated and different reagents are required. A potential alternative for conversion coating of copper is 5-methyl-1H-benzotriazole.
71 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Corrosion resistance: When tested at laboratory scale, the results according to internal specifications were equal compared to the chromium trioxide-treated substrate. To date, benzotriazole-mixtures are not technically feasible alternatives to replace chromium trioxide- based conversion coating processes as only laboratory testing has been completed, meaning that the alternative is at a very early developmental stage. R&D at production scale is ongoing.
One-step process Corrosion resistance Industrial upscaling (Pickling+conversion coating)
7.1.7.3 Economic feasibility Based on the early stage of development, no detailed analysis of the economic feasibility has been performed. However, it was stated that investments are needed for collecting waste containing 5- methyl-1H-benzotriazol, as it cannot be discharged to the on-site sewage treatment plant due to its complexing properties. Importantly, the former one-step process has to be adapted to a two-step process.
7.1.7.4 Reduction of the overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative, 5-methyl- 1H-benzotriazol would be the worst case with a classification as Acute Tox. 4, Skin Irrit. 2, Skin Irrit. 2 and STOT SE 3. As such, a transition from chromium trioxide – which is a non-threshold carcinogen – to this substance would constitute a shift to less hazardous substances.
7.1.7.5 Availability Application of 5-methyl-1H-benzotriazol was stated to be under investigation during the consultation phase. Industrial up-scaling was not started yet and the product is in laboratory phase. For full internal upscaling at least 3 years of development are necessary, assuming that no major drawbacks occur. As previously mentioned, the pre-treatment step also has to be developed simultaneously, increasing the uncertainties for the estimates mentioned here. Thereafter, for client approval and implementation into the supply chain, another 5 years would be anticipated. In summary, at least 8 years of R&D are necessary until the alternative could be fully industrialized.
7.1.7.6 Conclusion on suitability and availability for benzotriazole-based processes 5-Methyl-1H-benzotriazol was found to be a promising alternative for chromium trioxide in conversion coating of copper. The step involving pickling of the copper has to be simultaneously developed with another substance. Since these systems are in early research stages, for substitution of chromium trioxide at least 8 years are anticipated until the alternative products could be implemented into the supply chain.
7.1.8. ALTERNATIVE 8: Physical vapour deposition (PVD) PVD (Physical Vapour Deposition) was stated to be a promising alternative for the passivation of copper foils, as the main performance parameter can be met with this process. This alternative is assessed in detail in the following paragraph. Other tested substances or techniques clearly not meeting the requirements from this industry sector were classified as Category 3.
72 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.8.1 Substance ID and properties This vaporizing of the coating material may be conducted by one of the following methods: Vacuum evaporation: The coating (source) material is thermally vaporized in a vacuum and follows a “line-of-sight” trajectory to the substrate where it condenses into a solid film. Vacuum evaporation is used for applications such as mirror coatings and barrier films on flexible packaging (TURI, 2006). Sputtering: This process is a non-thermal vaporization where the surface atoms on the source material are physically ejected from the solid surface by the transfer of momentum from bombarding particles. Typically the particle is a gaseous ion accelerated from low pressure plasma or from an ion gun (TURI, 2006). Possible PVD coatings, applied as single or multi-layer, are based e.g. on the following materials: titanium nitride (TiN), titanium-aluminium nitride (TiAlN), zirconium nitride (ZrN), chromium nitride (CrN), chromium carbide (CrC), silicon carbide (SiC), titanium carbide (TiC), and tungsten carbide (WC). An overview of general information on exemplarily chosen substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.8.
7.1.8.2 Technical feasibility Traditional PVD coatings e.g. TiN and CrN are used for several applications like decorative surfaces, plumbing fixtures or to create “lifetime coatings” on door hardware (Legg K, 2003a, 2012). In this section, PVD-based processes are assessed as alternative for the following chromium trioxide-based surface treatment.
Table 17: Chromium trioxide-based surface treatments where PVD may be an alternative.
Industry sector Surface treatment Substrate / coating
General engineering Passivation Copper foils
The properties of most common PVD coatings are listed in the following Table 18.
Table 18: Material properties of typical PVD coatings (Legg K., 2003a)
Materials: TiN, TiAlN, ZrN, CrN, CrC, DLC, SiC, TiC
Property Value Note
hardness 1200 – 2400 depends on material and internal stress Vickers Hardness (HV) max. thickness 5 µm in rare cases up to 15 µm (high internal stress) corrosion resistance Moderate limited by pinholes wear resistance Excellent better than chrome, wear life can be low thin layers stress and effect of strongly thickness- PVD coatings generally have very high compressive stress. Fatigue fatigue dependent is usually adversely affected at coating thickness above a few microns. porosity < 1 % limited by pinholes
73 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Vacuum/Geometry: The need of a vacuum chamber limits the size and the type of parts that can be coated. PVD is a line of sight process that is not suitable for complex geometries and large parts, and is limited by the gun nozzle and the spraying angle. Deposition rate: According to information provided during the consultation, PVD processes show considerably lower deposition rates compared to chromium trioxide-based plating (a few µm per hour). In combination with the high costs of PVD equipment (see chapter 7.1.8.3), the coating costs rise with increasing coating thickness. The process speed is not in line with specifications from industry, where a maximum of 20 seconds per dipping process are required for chromium trioxide- based bath passivation. It is questionable if this technique is suitable for serial production, due to a low deposition rate of the coating material. Process conditions: PVD coatings, which are directly applied on the substrate without a preparing lacquer, are highly sensitive to contaminants (e.g. water, oils and paints) on the surface to be coated, thus require an atomically clean surface. Inadequate or non-uniform ion bombardment leads to weak and porous coatings and is the most common failure in PVD coating (Legg K., 2003). Layer thickness: In most cases the ion bombardment during coating causes high internal stress. This stress raises with increasing coating thickness and can lead to delamination of the coating. As a consequence, typical PVD layers are about 3–5 µm (in rare cases about 15 µm) thick, which is not in accordance with the industry requirements. Heat resistance: The process conditions for PVD require sub-atmospheric pressure and temperatures between 150 and 600°C. Process temperature, especially the upper limit, imposes restriction to the substrate materials that can be coated. Substrates where the maximum processing temperatures are below the temperature required for the PVD process, such as aluminium alloys (< 150°C) and high strength steel (< 250 C), are not suitable. For copper foils, the process conditions may be suitable. Corrosion: PVD nitride coatings are reported to be essentially inert and do not corrode. However, they do not provide as much corrosion resistance as chromium coatings do. Especially once the coating is scratched or damaged, the corrosion protection provided by the layer degrades compared to hard chrome layers. As reported from the industry, the corrosion requirements for passivated copper foils can be met. After one year, no oxidation was observed upon visual inspection. Furthermore, the passivated copper fulfils the specifications for heat resistance that require no oxidation after a 2 h thermal cycle at 200°C.
Corrosion resistance Heat resistance Deposition rate Layer thickness
7.1.8.3 Economic feasibility The technology for PVD processes differs fundamentally from the usual passivation processes with regard to the equipment and peripherals. Completely new production lines would need to be implemented as the PVD-based process cannot be performed in existing coating installations. The costs for a completely new plant including machine lines are estimated to be about €1-3 million for the coating system, with additional costs for cleaning lines (Legg K., 2012). During the consultation, the investment costs for PVD processes were commented by several companies to be very high while the implementation of the process represents a major business risk. As a consequence, PVD-based technology has clearly significant disadvantages from an economic point of view, as not only extensive investment costs occur, but also the process speed and production costs are not comparable to existing production lines.
74 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.8.4 Reduction of overall risk due to transition to the alternative As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Most material used in PVD are nitrides or carbides of transition metals. As toxicological worst case scenario, silicon carbide is classified as Carc. 1B, STOT RE (Specific target organ toxicity, repeated exposure) 1, Skin Irrit. 2, Eye Irrit. 2, STOT SE 3. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to a less hazardous substance. However, as at least one of the alternate substances is itself classified for mutagenicity and carcinogenicity, any replacements will need to be carefully evaluated on a case by case basis.
7.1.8.5 Availability PVD process equipment is commercially available to date. Vendors of PVD coating material (such as TiN) are found in most areas of the world. Different PVD-based processes have been tested within various industry sectors. R&D is ongoing, as PVD-based alternatives constitute promising alternatives from a technical point of view. However, at the current stage of development there are clear technical deficiencies regarding deposition rate and layer sickness and no process is available that meets the requirements for the passivation of copper foils.
7.1.8.6 Conclusion on suitability and availability for PVD At the current stage, coatings applied by PVD are technically not equivalent to chromium trioxide- derived products and do not present a general alternative. However for the passivation of copper foils, the required performance with regard to corrosion and heat resistance can be met. Major drawbacks of PVD-based applications are the thicker layer and the comparably slow deposition rate of the coating, making the whole process highly inefficient and therefore not applicable for this industry sector. Besides the technical failure, the PVD process differs fundamentally from current techniques for the passivation of copper foils, which would result in sector wide high investment costs if implemented to provide sufficient coating capacities. In addition, the production costs were calculated to be two times higher compared to existing chromium trioxide-solutions. In conclusion, PVD coatings are considered to be a niche application for specific small and medium size components (commercially available) but are not general replacement technology for passivation of copper foils. Therefore, at least 10 years are necessary until replacement techniques without using chromium trioxide may be fully industrialised.
7.1.9. ALTERNATIVE 9: Other oxide-based coatings
7.1.9.1 Substance ID and properties Various processes are currently under thorough investigation within the steel processing industry as replacement for chromium trioxide-based grain oriented steel insulation. So far, industry identified two potential replacement techniques for this purpose, other oxide-based coatings and Cr(III)-based coatings. Another group of potential alternatives (vapour deposition-based techniques) was assessed and clearly found to be not suitable as replacement. To date, research focuses on other oxide-based coatings, since previous work on Cr(III) revealed unsatisfactory performance especially with regard to coating tension (see chapter 7.1.2.2.3 for details). An overview of general information on some relevant substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.9.
75 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.9.2 Technical feasibility Table 19: Sector specific overview on chromium trioxide-based surface treatments processes where other oxide-based coatings are evaluated
Industry sector Surface treatment Substrate / coating
Grain oriented steel General engineering Steel insulation
General assessment: It was stated during the consultation that the R&D phase on this replacement technology was recently completed. The exact composition of the alternative is confidential business information. In laboratory scale, feasibility of key performance parameters, coating tension and magnetic properties was successfully proven as described below. For other parameters, performance needs to be improved carefully during industrial upscaling. Coating tension: As a key performance parameter for this process, coating tension does meet the requirements (> 4Mpa) when tested at laboratory scale. The tension imparted to the steel by this kind of coating is satisfactory for this purpose. Magnetic properties: The magnetic properties, another crucial parameter for this process, must be in accordance with the specifications of industry. A reduced tension would lead to poor magnetic properties resulting in core losses. The steel sold to customers must have guaranteed magnetic properties in compliance with international standards (IEC 60 404, Epstein frame and single sheet tester). When treated with this replacement coating, magnetic properties are in line with industry standards.
Layer thickness: Layer thickness has a direct impact on the coating tension. Specifications of industry require between 3 – 5 µm. During industrial upscaling, adjustment is needed to reach the required coating tension to ensure good magnetic properties. An increased thickness is not only detrimental for the (thermo) optical properties, but also for increased dust generation during slitting operations, risk for burr generation and stacking factor (ratio between steel and coating which has to comply with the IEC 60 404 standard).
(Thermo) optical properties: It was stated during the consultation that the replacement technology has a different visual aspect compared to the current industry standards (e.g. IEC 60 404), which is not in line with customer demands. To date, this is the major drawback of this replacement.
Machinability: Since this process uses other oxide particles than the current chromium trioxide-based standard, the hardness will increase, which will have an impact on burr height and cutting tool wear. If the hardness of the coating is too high, deburring will be cost-, time-, and material-consuming taking also the wear of the cutting tools into account. This will be subject to tests on internal industrial scale and in selected customer trials.
Further important parameters, such as adhesion properties and electric insulation seem to be sufficient at laboratory scale. Also the heat resistance can be stated as sufficient, as long as phosphate- based coatings are used.
As mentioned at the beginning of this chapter, oxide-based coatings as a replacement technique is currently the preferred alternative for the steel-processing industry. At laboratory scale, key parameters seem to be sufficient, however, several adjustments will have to be made for successfully passing the industrial upscaling phase. A major drawback might be the different optical properties, which are not in accordance with customer demands.
76 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
(Thermo) Coating Magnetic Layer Heat Electric Machinability optical Adhesion tension properties thickness resistance insulation properties:
7.1.9.3 Economic feasibility Against the background of the early development stage of this alternative, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible. For grain oriented steel insulation, process costs are comparable to the current chromium trioxide-based coating.
7.1.9.4 Reduction of overall risk due to transition to the alternative Please note that the exact substance identity and composition of products used in this description is not known as this is confidential business information of suppliers.
7.1.9.5 Availability Extensive R&D has been ongoing for several years already for the evaluation of potential alternatives to grain oriented steel insulation. So far, industry identified two potential replacement techniques for this purpose, which are other oxide-based coatings or Cr(III)-based coatings. For the time being, research focuses on other oxide-based coatings, since previous work on Cr(III)-based coatings revealed unsatisfactory performance results especially with regard to coating tension. For optimization work and industrial upscaling, a minimum of additional 7-10 years would be necessary, if no major drawbacks occur.
7.1.9.6 Conclusion on suitability and availability for other oxide-based coatings Two replacement techniques are currently being evaluated by the steel processing industry. The preferred alternative, other oxide-based coatings, is in line with most industry specifications as tested at laboratory scale. However, several adjustments have to be made to successfully pass the industrial upscaling phase. Taking the additional R&D time into account to overcome the technical issues and the uncertainties of successful industrial upscaling of an alternative, about 7-10 years are necessary to fully implement a replacement technique and to ensure the quality needs of the highly demanding customers worldwide.
7.1.10. ALTERNATIVE 10: Low tin steel (LTS) As alternative for ECCS in the Packaging sector various different alternatives have been evaluated and are currently under investigation. An overview on the potential alternatives is illustrated in Table 20. For ECCS, mainly two applications are considered: lacquer-coated and polymer-coated products. The lacquer coatings are the main application, while polymer coatings are used in cases where the coil is coated on both sides (one side with lacquer, the other side with polymer). Although the exact market distribution of lacquered vs. polymer-coated applications is not known, the polymer-coated applications were stated to be a growing market.
Table 20: Overview on potential alternatives to Electrolytic Chromium Coated Steel (ECCS) for the packaging sector.
Tested alternative for ECCS Category Low tin steel (LTS) (with and without Cr(VI)-free liquid phase conversion Category 1 coating)
77 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Tested alternative for ECCS Category Silane/Siloxane coatings by vapour Category 2 deposition Category 3: -Properties of the coated surface regarding optics, porosity and adhesion Cr(III)-based coatings not comparable to ECCS and not sufficient. - Cr(III) baths are no suitable alternative due to difficult and unflexible line driving and bath management. Category 3 Polymers (not specified) - Resistance to retorting (sterilisation) is not sufficient: The direct application of lacquers leads to delamination during sterilization process Manganese-based alternatives Category 3: very early laboratory stage
7.1.10.1 Low tin steel with and without Cr(VI)-free liquid phase conversion coating
7.1.10.1.1 Substance ID and properties LTS contains less tin than “conventional” steel, for example in the range of 0.1 to 1 g/m². LTS is no chemical substance and therefore no distinct hazardous classification and labelling information can be provided.
7.1.10.1.2 Technical feasibility LTS was tested as alternative to ECCS and from various LTS types: tin coating weight between 0.5 and 1.0 g/m², reflown versus non-reflown LTS, and LTS with optional nickel-flash. The technical details presented below are derived from the final report (Marmann, 2013) of the ISPA R&D project, performed by companies of the Steel and Packaging sector. The different surfaces were compared to ECCS in applied studies and then coated by different lacquers and polymers reflecting the broad applications of ECCS in the European market. The samples had to pass several tests on their mechanical behaviour, while in parallel, the new treatments (different kinds of conversion coatings) were evaluated towards their ecological and economical risks and chances to replace ECCS, including also food sector approval issues. Adhesion & Sterilisation performance: According to Marmann (2013), reasonable results in terms of adhesion and sterilisation performance were obtained with non-treated, non-reflown TLS (NR-TLS) with standard packaging lacquers (epoxy-phenolic type) for lacquered applications. In general, non- reflown LTS (NR-LTS) with a tin coating weight of 0.5 g/m² was found to be the substrate that performed best of all tested variations. In many aspects of product performance, in particular sterilisation resistance and lacquer adhesion after deformation, NR-LTS is comparable to ECCS. However, further optimisation of NR-LTS for lacquered applications is necessary by studying, for instance, iron-tin alloying kinetics, tin oxidation phenomena on LTS and by optimising the passivation system for LTS.
78 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Figure 12: Overall lacquer adhesion performance of IPSA materials expressed as “defect rate” on a scale from 0% (excellent) to 100% (very poor) (Marmann, 2013).
For polymer-coated applications, LTS does not provide a suitable alternative, since both reflown and non-reflown LTS show extremely poor adhesion of the polymer film after DRD (draw-redraw deformation) (Marmann, 2013). To improve its adhesive performance, especially for polymer coatings, LTS was assessed with various subsequent chromium-free liquid-phase conversion layers (such as phosphate, titanate, silicate, acrylate and silane-based systems) as intermediate layer (between the LTS and the polymer coating). In Figure 12, results of lacquer adhesion tests of non- treated LTS (Non-tr), LTS samples with subsequent conversion coating and ECCS are listed. The used conversion coatings are anonymized by capital letters and numbers. C2 coatings are conversion coatings based on silane/inorganic, C3 are silicate/silane-based conversion coatings and H5 are Ti/Zr- based conversion coating. The results of lacquer adhesion tests showed that ECCS has a defect rate of around 5%, while all other alternatives clearly performed much worse. Non-treated, non-reflown LTS (the most left green bar) gives the best adhesion performance (defect rate of < 15%) and is performing nearly as well as ECCS. In general, reflown LTS (yellow bars) gives poor results and the application of liquid adhesion systems does not contribute significantly to improve adhesion performance. In many tested cases, the non-treated NR-LTS showed the best performance. The most promising liquid phase adhesion systems are based on silicates/silanes (C3) and titanium/zirconium (H5). LTS shows unexpectedly high tin oxide growth, and the investigated liquid-phase adhesion systems do not sufficiently passivate the surface in case of LTS samples with a CSC (cathodic soda carbonate) pre-treatment before liquid adhesion system application. As stated during the consultation, LTS require a high durable passivation and conversion layer to prevent these effects. However, no adequate solution for this has been found yet. Food safety: According to Marmann (2013), a first food safety evaluation has been performed within the IPSA R&D project for LTS with different kinds of conversion coatings. For the Ti/Zr-based coating, the system was considered not to be harmful to health and thus complying with Article 3 of the Framework Regulation (EC) 1935/2004. For other systems, more information is required and a final assessment cannot be given at the current stage of R&D. Conclusion: In summary, LTS – either untreated or with subsequent liquid phase conversion coating – is investigated as alternative to substitute lacquered and polymer coated ECCS and are found to be a promising concept. With regard to lacquered substrates, reasonable results in terms of adhesion and sterilisation were obtained with non-treated, non reflown LTS with standard packaging lacquers
79 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
(epoxy-phenolic acid) but further optimisation is necessary. For polymer-coated applications, LTS does not provide a suitable substrate. Both reflown and non-reflown LTS show extremely poor adhesion of the polymer film after deformation tests and no improvement could be obtained applying a chromium-free subsequent coating. In general, LTS is not yet a technical feasible general alternative for both lacquered- and polymer-coated ECCS applications.
Adhesion Sterilisation resistance Food safety
Sufficient only for lacquered Sufficient only for lacquered
substrates, not for polymer- coated substrates, not for polymer- coated
7.1.10.1.3 Economic feasibility Against the background of significant technical failure of this alternate system, no detailed analysis of economic feasibility was conducted. However, there are diverging opinions on the economic feasibility of LTS and for example, 3 to 4 times increased costs for the metallic coating step for the production of LTS compared to ECCS were stated during the consultation. A final assessment could not be made based on the early development of the alternative and dependency on the evolution of the price for tin.
7.1.10.1.4 Reduction of overall risk due to transition to the alternative The transition from chromium trioxide – a non-threshold carcinogen - to LTS would constitute a shift to less hazardous substances. However, depending on the final solution (including necessary passivation), the alternative has to be evaluated on a case by case basis.
7.1.10.1.5 Availability The R&D project IPSA launched by the European Commission and the General Directorate for Research and Innovation aimed to develop an alternative for ECCS. The project was finalized in 2013 and documented with a report of Marmann et al. (2013). The project showed reasonable results for non reflown tin steel (NR-TLS) for lacquered applications. For both application types, lacquer coated and polymer coated, further R&D is necessary to improve the performance. Although LTS is a promising concept, it is not a general alternative to ECCS for all kinds of applications (for example not for the beverage industry due to the presence of tin). At the current stage, the alternative for lacquered coatings is at laboratory stage (TRL 4), while the polymer coated application is expected to be even at a lower stage. As a consequence, further R&D is necessary on the technical issues with the alternative and it is considered to be a challenge to overcome the issues to make the alternative universal/general. Therefore it is not likely that LTS as alternative for ECCS in both application types will become technically feasible and industrially available within the next 10 years.
7.1.10.1.6 Conclusion on suitability and availability for LTS A large R&D project (IPSA) has been performed by major companies from the steel for (food) packaging industry on the functionalities of LTS substrates. As a conclusion, LTS is not a general alternative to ECCS for all kinds of applications (lacquered and polymer coated). For example LTS would not be an option for the Beverage industry due to the presence of tin. NR-LTS showed reasonable results for lacquered applications regarding adhesion properties and sterilisation resistance, but numerous other functionalities have to be investigated and improved. For polymer coated applications, none of the tested LTS, either with or without coating, was found to be technically sufficient. The development of the alternative is at TRL 4 or even lower and further intensive R&D is necessary. It is not expected that the alternative becomes technically feasible and industrially available as a general alternative for ECCS within the next 10 years.
80 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.1.10.2 LTS with silane/siloxane Coatings (CVD)
7.1.10.2.1 Substance ID and properties Different kinds of metal substrates, such as stainless steel and LTS, can be coated by a silica film of SiO2 applying silane and siloxane coatings. Silane and siloxane coatings are described in detail in chapter 7.2.3 (Silane/Siloxane and Sol-Gel coatings). For applications in the food packaging sector, the most promising silane is TEOS (tetraethylorthosilane) and the most promising siloxane is HMDSO (hexamethyldisiloxane). The substances are applied by vapour deposition, typically chemical vapour deposition (CVD). CVD uses gases that, combined on a hot surface, form a hard coating (TURI, 2006). The process temperature ranges between 800 and 1000°C. CVD coatings have a good adhesion behaviour. The surface of CVD coated parts is rough and microporous. A non-exhausting overview of general information on substances used within this alternative and the risk to human health and the environment is represented within Appendix 2.1.10.
7.1.10.2.2 Technical feasibility General assessment: The performance of CVD coatings based on silanes and siloxanes was tested as part of the IPSA R&D project. The performance of silica (SiO2) deposited by using the precursors TEOS and HMDSO on different substrates (stainless steel, tin plated steel, LTS) was assessed and adjusted during different tests, including lab scale bench tests. According to Marmann (2013), silica films exhibit a minimum film thickness of 12 nm and showed good barrier properties in several tests (e.g. cysteine discolouration, constant climate corrosion). The loss of adhesion at the interface tin /silica film after tempering could not been resolved. The latest silica film used in the lab scale test (formed from HMDSO) showed very high deposition rates and good adhesion on stainless steel, however, the transfer to LTS sheets could not be performed until the end of the R&D project due to plasma source fail (for example too high consumption of plasma gas). This issue needs to be investigated by further R&D. An investigation of all investigated samples regarding coating weight, tin oxide, surface energy, lacquer adhesion and barrier properties against sulphur (sulphur staining resistance) was performed showing that most of the samples have good wettability (high surface energy) and high barrier properties. However, for all different variants, the lacquer adhesion performance was clearly lower compared to ECCS (Marmann, 2013). In general, none of the investigated gas phase deposited oxide films on LTS have the same performance as ECCS. This is especially the case regarding lacquer adhesion even without further deforming and sterilisation. The size of the samples could not be scaled up to realize application and testing in at least small pack tests for the different polymer and lacquered samples. Therefore, none of the variants will be further investigated (Marmann, 2013).
Lacquer adhesion Wettability Sulphur staining resistance
7.1.10.2.3 Economic feasibility Against the background of significant technical failure of this alternate system, no detailed analysis of economic feasibility was conducted. However, based on the literature research and consultations, there is no indication that the discussed alternative is not economically feasible. It was also stated
81 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
during the consultation that longer reaction times (curing) lead to increased costs (line speed, energy input).
7.1.10.2.4 Reduction of overall risk due to transition to the alternative Classification and labelling information of substances and products reported during the consultation was reviewed. In addition, publicly available information on specific alternative products was evaluated (please refer to chapter 7.2.3.4 - Alternative 3 Silane/Siloxane and sol-gel coatings). Transition from chromium trioxide – which is a non-threshold carcinogen – to a TEOS- or HMDSO- based coating would constitute a shift to less hazardous substances.
7.1.10.2.5 Availability
The performance of silica (SiO2) deposits using the precursors TEOS (tetraethylorthosilane) and HMDSO (hexamethyldisiloxane) on different substrates (stainless steel, tin plated steel, LTS) was tested and adjusted in different tests in the IPSA R&D project. No technical feasible alternative was found at the end of the R&D project and the development was stopped at TRL1. Due to the unsatisfactory results and more promising alternatives, no further R&D on this alternative is planned.
7.1.10.2.6 Conclusion on suitability and availability for LTS with silane/siloxane coatings Silane or siloxane-based coatings applied by CVD were tested and found not to be technically feasible as alternative to ECCS. In general, none of the investigated gas phase deposited oxide films on LTS has the same performance as ECCS. This is especially the case regarding lacquer adhesion independent of further deforming and sterilisation. No further R&D on these alternative is performed, as the technical results were unsatisfactory.
7.2. Pre-treatments After several alternatives for the main surface treatment have been assessed in the former chapters, the following chapters concentrate on alternatives for the pre-treatments like etching, pickling, deoxidizing, and stripping. As already stated in chapter 3.2, only the combination of processes applied in sequence (pre- treatment, main process step and post-treatment) is able to provide the coating with the required functionalities. Although the single process steps can be assessed individually, they are not stand- alone processes but part of a process chain or process flow.
7.2.1. Inorganic acids
7.2.1.1 Substance ID and properties A variety of inorganic acids are currently under evaluation as alternatives to chromium trioxide in surface pre-treatment processes. Research currently focuses on sulphuric acid, phosphoric acid, nitric acid and a mixture of sulphuric acid, nitric acid, and ferric ions from iron sulphate (named “sulfonitroferric acid”). An overview of general information on substances used within this alternative and the risk to human health and the environment is provided in Appendix 2.2.1. 7.2.1.2 Technical feasibility Table 21 summarizes the chromium trioxide-based surface pre-treatment processes where inorganic acids may be an alternative:
82 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Table 21: Overview on the replacement substances used in the different pre-treatment processes
Surface treatment Substrate / coating Alternative
Aluminium and aluminium alloys, Mixture of sulphuric acid, nitric acid, and ferric ions Functional cleaning/ (stainless) steel, (“sulfonitroferric acid”), mineral acids Pickling/Etching/ copper, brass, desmutting molybdenum Steel Mineral acids, electrolytic pickling Electropolishing Steel Mineral acids Aluminium and Mixture of sulphuric acid, nitric acid, and ferric ions Deoxidising aluminium alloys, (“sulfonitroferric acid”) Aluminium and Stripping of organic aluminium alloys, Mixture of sulphuric acid, nitric acid, and ferric ions and inorganic finishes Magnesium and (“sulfonitroferric acid”) magnesium alloys
Pickling/etching/desmutting – pickling/etching of metal surfaces (e.g. aluminium alloys, copper, brass, molybdenum) General assessment: For metallic substrates such as aluminium alloys, alternatives based on either nitric acid, sulphuric acid, phosphoric acid, or combinations together with ferrous ions from iron sulphate (sulfoferric, sulfonitroferric) are at the developmental stage and partly introduced and qualified for pickling at some companies. With this treatment, moderate oxide removal can be performed. These pickling/etching solutions are significantly more aggressive than the Cr(VI)-based one, causing higher degrees of end grain pitting and intergranular attacks. For moderate cleaning purposes, a less aggressive solution is needed. Compared to pre-treatments on steel, where surface characteristics for subsequent bonding are the most critical requirement, the surface preparation of Al and its alloys includes other issues. The treatments applied for preparation of aluminium surfaces currently involve multiple steps containing chromium trioxide, as described in the introduction. Generally, the performance of the subsequent treatments after pickling/etching is strongly linked to the, robust and validated, combination of pre- treatment processes, and to the type / chemical composition of the Al alloy being processed. A mixture of “sulfonitroferric acid” is already qualified and implemented for surface preparation prior to CAA, TSA, SAA, PSA and chemical conversion coating on aluminium alloys for some specific applications in the aerospace sector. It is approved prior to fusion welding, prior to brazing, and for removal of foreign metal contamination. Alkaline etching with sodium hydroxide containing additives, and acid etching with solutions of nitric acid containing fluoride from hydrofluoric acid or ammonium bifluoride are acceptable alternatives to chromium trioxide-based etching solutions used for aluminium, and alkaline etching is preferred for etching aluminium alloys. These substances cannot currently be seen as general alternatives though but are only suitable on some metal alloys or for some applications. It was stated during the consultation that these solutions are not suitable for removal of welding and brazing flux. They are clearly not suitable for localized repairs and to steel substrates. For other substrates, such as copper or brass, phosphoric and fluoride acid solution can be added for heavy oxides removal, and this solution may become technically feasible after further development. For Al alloys, this treatment is not adequate, due to the comparatively more aggressive character of the treatment, as explained in the first paragraph. For pickling/desmutting of molybdenum, chromium trioxide-free smut removal has proved to be very challenging over the last years. Several proprietary mixtures of sulphuric acid plus additives (e.g.
83 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Cr(III), NaF, Ammonium bifluoride) were tested and clearly found to be insufficient as the smut was resistant and could not be removed. In first laboratory tests, hydrogen peroxide plus ammonium bifluoride showed promising results, although it potentially etches the surface detrimentally if the process is not monitored very carefully. Furthermore, a two-step trial with KMnO4 and Potassium Peroxomonosulphate has been conducted once, but the initial results were not promising. Here, further experiments with varying times, concentrations and temperatures have to be carried out within the next years. Process development and Compatibility: Some of the newly developed and partly implemented alternatives are already in use for some applications within other industry sectors not covered within this dossier. Importantly though, these alternatives do not prepare the surface equivalent to chromium trioxide-based processes. As a consequence, extensive analysis and adjustments of the whole process chain had to be performed until these products were approved. The main issue is that measurable parameters rarely exist for the performance of the pre-treatment alone, so that standard tests mainly have to be performed on the final coating. At this stage, it very challenging to evaluate which part of the process chain is influencing the surface characteristics of the final coating. Taking all the different applications and alloys used throughout the different industry sectors into account, it must be stated that substantial efforts are still needed to implement and adjust the existing pre-treatment chains to the chromate-free alternatives, in order to meet the specifications of the respective industry sector. In summary, implementation of alternative pre-treatments is highly complex and depends on multiple factors. As the pre-treatment steps are all linked to each other and to the performance of the final coating, new processes have to be analysed with regard to potential reaction by-products or impurities influencing subsequent steps or different surface characteristics derived from alternative pre- treatments.
Pickling/etching/desmutting – pickling of steel General assessment: During the consultation phase it was stated that R&D is ongoing for the use of mineral acids as alternative to pickling of steels with chromium trioxide. The pickling of stainless steel with a mixture of nitric acid and hydrofluoric acid is used as a standard process within some industry sectors, e.g. aerospace. The same applies for pickling of low alloy steels with different mineral acid-based solutions. Currently these alternatives cannot be used for low alloy steels though, as the main criterion for these pre-treatments, a sufficiently prepared surface for optimal adhesion of the subsequent layers, is not fulfilled. Additional R&D is necessary to develop appropriate replacement solutions. For desmutting of stainless steels from 301-, 302- and 304-type, trials based on mineral acids (Sulfuric acid, hydrochloric acid) showed unsatisfactory results with regard to smut removal and reproducibility. In first laboratory tests, hydrogen peroxide plus ammonium bifluoride showed promising results, although it potentially etches the surface detrimentally if the process is not monitored very carefully. Furthermore, a two-step trial with KMnO4 and Potassium Peroxomonosulphate with varying times, concentrations and temperatures will be carried out within the next years. For pickling before bonding of stainless steels, sulphuric acid electrolytic pickling can also be applied. The metal substrate is the cathode (or the anode, depending on the steel type and exact process) in an electrolytic cell containing a strong acidic solution, such as sulphuric acid, which dissolves the oxide layer. During the consultation phase it was stated that laboratory scale testing demonstrated the technical feasibility of the process step for pickling of stainless steel prior to bonding with chromate- free solutions, but the need for further chromium trioxide-based pre-treatments remains. Industrial up-scaling to demonstrate the suitability of the chromium trioxide-free process chain still has to be conducted. In conclusion, neither sulphuric acid pickling of steel before bonding nor electrolytic pickling are currently alternatives to chromium trioxide-based pickling pre-treatment processes, but
84 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES the alternatives have shown their technical feasibility in laboratory scale testing and further R&D has to be performed. Electropolishing An alternative is currently under development for Electropolishing, a process used to remove flaws or debris from the surface of a metal substrate. Within this pre-treatment on steel, chromic acid is needed for buffering the solution, elimination of impurities from thermal treatments and most importantly, improve the fatigue properties of structural parts. As a replacement technology, several alternative acids (chlorohydric, phosphoric or phosphoric/sulfuric acid) are currently under investigation and are qualified only for localized repair applications on stainless steel. In general, they are not an acceptable solution as the martensitic steel will become fragile after this treatment, generating inter granular corrosion that will lead to part rupture. Deoxidising General assessment: Current R&D studies revealed mineral acid-based deoxidiser solutions as a potential alternative for special applications within different industry sectors. They are already partly implemented for some applications. The deoxidising causes a dissolution of aluminium oxides, which is in line with specifications of the aerospace sector. Furthermore, visual inspection of the appearance of the deoxidised surface (after rinsing) revealed a water break free surface without streaks or discolouration. End grain pitting and intergranular attack: This parameter is within the required ranges for some sectors, but experience in other sectors indicates that failures periodically occur with aged solutions. This can require premature disposal of deoxidising solutions and result in unplanned downtime and possible rework in the processing facility. Corrosion resistance: It was stated during the consultation that these alternatives are within the required ranges for some applications but do not meet the requirements for corrosion protection, when used prior to sealed anodizing or conversion coatings. Corrosion resistance failures occur intermittently with aged solutions in these applications. This can require premature disposal of deoxidising solutions and result in unplanned downtime and possible rework in the processing facility. When corrosion protection is not a requirement (e.g. as pre-penetrant etching/desmutting and deoxidizing prior to unsealed anodizing), this solution might be used as alternative to chromium trioxide-based deoxidisers. Process development and Compatibility: As for alternatives to pickling/etching, the same limitations and concerns apply for the implementation of alternative deoxidizing solutions. As mentioned, some of the newly developed and partly implemented alternatives are already in use for some applications within other industry sectors not covered within this dossier. Importantly, these alternatives do not prepare the surface equivalent to chromium trioxide-based processes. As a consequence, extensive analysis and adjustments of the whole process chain had to be performed until these products were approved. The main issue is that measurable parameters rarely exist for the performance of the pre- treatment alone, so standard tests have to be performed mainly on the final coating. At this stage, it is very challenging to evaluate which part of the process chain influences the surface characteristics of the final coating. Taking all the different applications and alloys used in the different industry sectors into account, it must be stated that substantial efforts are still needed to implement and adjust the existing pre-treatment chains to the chromate-free alternatives, in order to meet the specifications of the respective industry sector.
85 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
In summary, the proposed solutions are not suitable as general alternative but can only be used for specific applications (e.g. heavy duty deoxidising) where no corrosion resistance is required. Stripping of inorganic finishes It was stated during the consultation phase that for each kind of inorganic finish, such as hard anodic coatings and conventional anodic coatings, spray coatings and conversion coatings, individual stripping alternatives have to be developed, while the current chromium trioxide-based stripping can be used for all substrates and inorganic finishes without differentiation. For some applications on external metallic and customized surfaces on Al alloys, stripping alternatives-based on benzyl alcohol (with or without acid, and / or peroxide), or solutions with formic acid are qualified and used. However, for other applications these products are currently not suitable. General assessment: Current R&D studies revealed a mineral acid-based solution of sulphuric acid and nitric acid with iron sulphate as a potential alternative for the stripping of conversion coatings and anodic coatings from aluminium alloys (but clearly not for the above mentioned hard anodic and thermal spray coatings). These solutions are stated to meet the requirements in general, but with severe limitations. Key parameters: With regard to residual stress, the alternative solutions potentially etch the surface of the parts which can then cause residual stress. A short immersion time of the material to be stripped has to be guaranteed, this is required to avoid impacting residual stress, surface roughness or causing intergranular attack, which can affect the fatigue properties. The short immersion time is also necessary to avoid excessive removal of base material. The corrosion requirements are clearly not met for applications where assemblies with dissimilar metal components are used. Here, alternative stripping methods would get in contact with materials they are not suitable for. This would increase the risk for galvanic corrosion between the different metals. Besides high strength steel components, (for which the alternative is not applicable in general), other sensitive parts have to be protected prior to the application of the stripping alternative. From a safety point of view, it may be considered that for solutions containing peroxides severe chemical reaction can take place when the process is not properly controlled. For steel substrates, iron can be dissolved from the metal which may lead to explosive decomposition of Hydrogen peroxide.
In conclusion, these solutions may be technically feasible for some applications but are limited to stripping of conversion coatings and anodic coatings from aluminium alloys, when the respective process control and short immersion time is guaranteed. Nevertheless, it is not a general stripping alternative for the large variety of inorganic coatings and substrates within this use.
7.2.1.3 Economic feasibility For the tested alternatives, no detailed analysis of the economic feasibility was carried out, as they are not qualified throughout all industry sectors and can currently not be seen as general alternatives. It was stated during the consultation phase that electrolytic pickling is expected to be more expensive than chromium trioxide-based pickling processes when considering investments needed. However, based on the literature research and consultations there is no indication that the discussed alternatives are not economically feasible. 7.2.1.4 Reduction of overall risk due to transition to the alternative As the alternatives are not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (see Appendix 2.2.1), nitric acid would be the worst case with a classification as Ox. Liq. (Oxidising
86 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES liquid) 3, Skin Corr. 1A, Met. Corr. 1, Skin Irrit. 2, Eye Dam. 1, STOT SE 3. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances. 7.2.1.5 Availability Several alternatives based on mineral acids are available for all types of pre-treatment steps on different substrates. Still, no suitable alternative is available for all types. Some of the newly developed and partly implemented alternatives are already in use for some applications within the different industry sectors. As stated, these alternatives do not prepare the surface equivalent to chromium trioxide-based processes. As a consequence, extensive analysis and adjustments of the whole process chain had to be performed until these products were approved. The main issue is that measurable parameters rarely exist for the performance of the pre-treatment alone, so standard tests have to be performed mainly on the final coating. At this stage, it is very challenging to evaluate which part of the process chain influences the surface characteristics of the final coating. Taking all the different applications and alloys used in surface treatment for miscellaneous sectors into account, it must be stated that substantial R&D efforts are still needed to implement and adjust the existing pre-treatment chain to the chromate-free alternatives, in order to meet the specifications of the different industry sectors. 7.2.1.6 Conclusion on suitability and availability for inorganic acids In summary, for pickling/etching of steel as pre-treatment processes, alternatives for some applications are technically feasible, while currently no generally acceptable replacement exists. For some steels and other substrates, development is currently of low maturity. For chromate-free pickling/etching pre-treatment on aluminium and its alloys, a mixture of sulphuric acid, nitric acid, and ferric ions are commercially available and qualified for some anodizing applications on Al alloys. Since the alternative is technically not yet equivalent to the current process, further R&D is necessary. For localized repairs on anodized layers, the etching step needs to be adapted to each Al-alloy. As a consequence, further development on chromate-free etching/pickling pre-treatment is necessary before the alternative can become broadly deployed throughout all industry sectors, especially as any change of pre-treatment has to be carefully adapted to the subsequent process. Although certain pre- treatments may already be used within the different sectors, these are part of a process chain and at the current stage, a chromium trioxide containing subsequent treatment has to be applied, to fulfil the demands of the respective sector.
Technical feasibility Economic feasibility Risk reduction Availability
Qualified for specific Qualified for specific applications in some applications in some parts of the industry parts of the industry
7.2.2. Pickling/Etching of copper
7.2.2.1 Substance ID and properties For pickling of copper, two alternatives are currently under evaluation, as summarized in Table 22. An overview of general information on substances used within this alternative and the risk to human health and the environment is provided in Appendix 2.2.2.
87 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
7.2.2.2 Technical feasibility Table 22 summarizes the chromium trioxide-based surface pre-treatment processes where the following substances may be an alternative: Table 22: Overview on the replacement substances used in the different pre-treatment processes
Surface treatment Substrate / coating Alternative
Ammonia/ ammonium chloride Pickling/Etching copper Sodium/ammonium persulfate with sulphuric acid
Pickling/etching General assessment: The laboratory scale tests for both alternatives were successful and the next step is testing on larger scale. Both alternatives revealed a micro roughness which was equally homogenous compared to chromium trioxide. The density and depth of the caverns was sufficient. Process engineering: For spray etching using ammonia/ ammonium chloride, the bath needs to be adapted (stainless steel to be replaced by titanium) or a new bath needs to be put in place since ammonia corrodes the steel constructions of the building. Another issue with ammonia is the toxicity and subsequent compliance with emission regulations. Safety measures need to be in place and the process needs to be segregated/closed. Furthermore, gas washers are needed before release to outside air.
When a mixture of sodium persulfate and H2SO4 was used, a drawback is that the persulfate starts degrading after 2 weeks, so regular replacement is necessary. Instead of sodium persulfate, ammonium persulfate can be used, which gives a better pickling result, but may affect the on-site waste water treatment plant (WWTP). Pickling mixture and rinsing water would need to be collected and cannot go into the on-site WWTP.
7.2.2.3 Economic feasibility For the tested alternatives, no detailed analysis of the economic feasibility was carried out, as they are not qualified currently as general alternatives. However, when discussing ammonia as potential alternative, major investments have to be carried out to protect people, the internal environment and the outdoor environment from the adverse effects. Furthermore, it is a complexing agent and thus cannot be released to the on-site WWTP. 7.2.2.4 Reduction of overall risk due to transition to the alternative As the alternatives are not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (see Appendix 2.2.1), nitric acid would be the worst case with a classification as Ox. Liq. 3, Skin Corr. 1A, Met. Corr. 1, Skin Irrit. 2, Eye Dam. 1, STOT SE 3. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances. 7.2.2.5 Availability Large scale testing has not yet started for any of the alternatives tested. For ammonia, a safety-health- environment study will be done to analyze its impacts.
88 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
As stated in chapter 7.1.7.2 , pickling and passivation of copper can currently be done in a single step process using chromium trioxide. As none of the available alternatives is able to provide the same properties, the process has to be split into two separate treatments with different alternatives. Indeed, these potential alternatives have to be evaluated concomitantly, to evaluate if, with the combination of the alternatives, the required surface characteristics can be achieved. As a consequence, extensive analysis and adjustments of the whole process chain might need to be performed before these products could be approved. The required combined development lead to additional R&D efforts with increased uncertainties. Thereafter, to overcome the technical issues and for client approval and implementation into the supply chain in summary at least 8 years are necessary. 7.2.2.6 Conclusion on suitability and availability for pickling/etching of copper The tested alternatives for pickling/etching of copper were found to be promising alternatives for chromium trioxide in laboratory scale testing. The alternative for passivation of copper has to be developed with other substances simultaneously. Since these combined systems are in early research stages, for substitution of chromium trioxide a period of at least 8 years is anticipated until the alternative products could be implemented into the supply chain.
Technical feasibility Economic feasibility Risk reduction Availability
89 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
8. OVERALL CONCLUSIONS ON SUITABILITYAND AVAILABILITY OF POSSIBLE ALTERNATIVES For this AfA, an extensive literature survey and consultation with industry experts was carried out to identify and evaluate potential alternatives to surface treatments of metals with chromium trioxide such as aluminium, steel, zinc, magnesium, titanium, copper, alloys. Chromium trioxide-based surface treatments are specified by industry because they provide superior corrosion resistance and inhibition, improved paint adhesion, low electrical contact resistance and/or enhanced wear-resistance (see Chapter 3.3). These characteristics are generally essential to the safe operation and reliability of vehicles, equipment and machinery which operate under extreme conditions. On the other hand, while several potential alternatives to chromium trioxide are being investigated for different processes, substrates and treatment steps, results so far do not support reliable conclusions regarding their performance as part of such complex systems, in demanding environments and real-world situations. These potential alternatives do not support all the properties of chromium trioxide-based surface treatment systems, and their long-term performance can currently only be estimated. Decreased performance would necessitate shorter inspection intervals, with a substantial impact on associated maintenance costs. The chemistry behind surface treatment systems and processes using chromium trioxide is complex. Surface treatment processes typically involve numerous steps, often including several important pre- treatment and post-treatment steps as well as the main treatment process itself. These steps are almost always inter-related such that they cannot be separated or individually modified without impairing the overall process or performance of the treated product. This means it is imperative to consider the surface treatment system as a whole, rather than the step involving chromium trioxide on its own, when considering alternatives for such surface treatment systems. Furthermore, components that have been surface treated with chromium trioxide typically represent just one of many critical, inter- dependent elements of a component, assembly or system. In general, chromium trioxide-based surface treatment is specified as one element of a complex system with integrated, often critical performance criteria. Compatibility with and technical performance of the overall system are primary considerations of fundamental importance during material specification. 11 potential alternatives (including processes and substances for all parts of the process chain) are a focus for ongoing research and development (R&D) programs and are examined in further detail in this report. While several potential alternatives to surface treatments with chromium trioxide, predominantly Cr(III)- and organometallic-based, are being investigated for various substrates and treatment steps, results so far do not support reliable conclusions regarding their performance as part of such complex systems, in demanding environments and real-world situations. These potential alternatives do not support all the properties of chromium trioxide-based surface treatment systems, and their long-term performance can currently only be estimated. In summary, the analysis shows there are no technically feasible alternatives to chromium trioxide-based surface treatment systems for key applications. Several potential alternatives are subject to ongoing R&D, but do not currently support the necessary combination of key functionalities to be considered technically feasible alternatives. Assuming a technically feasible potential alternative is identified as a result of ongoing R&D, extensive effort is needed beyond that point before it can be considered an alternative to chromium trioxide within the different industry sectors. As for all sectors long-lasting approval processes exist, the industry anticipates the R&D programs, industrial upscaling and implementation into the supply chain will require at least another 10 years.
90 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Table 23: Summary of Findings of AoA (x marks technical failure, (x) marks failure not for all applications)
Potential experience Alternative (basis
Sector step process - Maturity of process &/or Adhesion term Robustness - Food Safety
coating) Machinability Coating tension Coating Reproducibility Layer thickness One Application speed Fatigue resistance Fatigue Magnetic properties Magnetic Corrosion resistance Corrosion Long Complex parts/geometry Complex
Performance Failure According to Critical Criteria / Functionality Architecture Acids x x Silane/siloxane x x x Organometallics (Zr, (x) (x) (x) (x) Ti) Cr(III) (x) (x) x Automotive Acids x x x Silane/Siloxane x x Cr(III) (x) x x Gen Engineering - PVD Passivation copper x x foil Gen Engineering Other oxides x x x - GOES insulation Cr(III) x x x Gen Engineering – Organometallics (Zr, x x conversion coatings Ti) Cr(III) (x) (x) x 5-Methyl-1H- x x benzotriazol Packaging - ECCS Low tin steel (LTS) x x LTS with Silane/ x Siloxane
A large amount of research over the last decades has been deployed to identify and develop viable alternatives to chromium trioxide-based surface treatment. Due to its unique functionalities and performance, it is challenging and complex to replace surface treatments based on chromium trioxide in applications that demand superior performance for corrosion and/or adhesion to deliver safety over extended periods and extreme environmental conditions. Several potential alternatives to chromium trioxide are under investigation across industry sectors. However, based on experience and with reference to the status of R&D programs, alternatives are not foreseen to be commercially available for key applications in these sectors for at least 8 -10 years. A review period of 7 years was selected because it coincides with optimistic estimates by the industry of the schedule required to industrialise alternatives to chromium trioxide. It also reflects the duration of the normal review period indicated by ECHA.
91 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
REFERENCES AMMTIAC (Advances Materials, Manufacturing and Testing Information Analysis Center) (2012): AMMT- 39 – Analysis of Alternatives to Hexavalent Chromium: A Program Management Guide to Minimize the Use of Cr(VI) in Military Systems, AMMT-39 by Lane, R.A., Fink, C. & Grethlein, C Alwitt, R.S., Liu, Y (2001) Electrically conductive anodized aluminium coatings. US Patent 622 82 41 B1 ECCA (2012): Coil Coating: Sustainable Process, Sustainable Products. Deresh, L. (1991): Composition and method for producing chromate conversion coatings. EP Patent EP 0451409 A1.
FAST Report (2009): Flight Airworthiness Support Technology - FAST 45. Airbus Technical Magazine. December 2009
GSB International (2012): Chromfreie Oberflächenvorbehandlung für Aluminium, Dokumentation des Stands der Technik, 2nd Edition, Editor: Alfort, H.J., Blecher, A. & Mader, W. GSB International (2013): Internationale Qualitätsrichtlinen für Beschichtung von Bauteilen aus Aluminium, Stahl und feuerverzinktem Stahl, Ausgabe Mai 2013, Stand 05.08.2013. Guan, Y., Liu, J.G., Yan, C.W. (2011): Novel Ti/Zr Based Non-Chromium Chemical Conversion Coating for the Corrosion Protection of Electrogalvanized Steel. Int. J. Electrochem. Sci., 6 (2011) 4853 – 4867
Hao, L. and Cheng, B.R. (2000): Sealing processes of anodic coatings: past, present and future. Aluminium Finishing 98 (12): 8–18.
Harvey, T.G., Hughes, A.E, Hardin, S.G., Nikpour, T., Toh, S.K., Boag, A., McCulloch, D. and Horne, M. (2008): Non-chromate deoxidation of AA2024-T3: Sodium bromate-nitric acid (20-60°C), Applied Surface Sciences 23: 3562-3575.
Lee, H.S, Kim, S.K., Sohn, H.J, Kang, T. & Kim, H.J (2002): Electrochemical properties of Permanganate- based conversion coatings on zinc. Meeting abstracts- Electrochemical Society; 2002-2; 16 Electrochemical Society Meeting; 202nd Lee, Y.L., Chu, Y.R., Li, W.C. & Lin, C.S, (2013): Effect of permanganate concentration on the formation and properties of phosphate / permanganate conversion coating on AZ31 magnesium alloy, Corrosion Science, 70, pages 74-81. Legg, K. (2003a): Chrome Replacements for Internals and Small Parts, final report (http://www.asetsdefense.org/documents/DoD-Reports/Cr_Plating_Alts/Cr_Rplcmnt-IDs&Sm_Parts.PDF) Legg, K. (2003): Chromium and Cadmium Replacement Options for Advanced Aircraft, HCAT Program Review, KSC. Legg, K. (2012): Choosing a Hard Chrome Alternative (http://www.rowantechnology.com/wp- content/uploads/2012/06/Hard-Chrome-Plating-Alternatives.pdf) Marmann, A., Spagnol, V., Penning, J.P (2013): Innovative packaging steel with enhanced adhesion to organic coatings based on nanostructured interphases (IPSA). Qualicoat (2012): Specifications for a quality label for liquid and powder organic coatings on aluminium for architectural applications, 13th edition http://www.qualicoat.net/qcsite/download/uk/13th%20EDITION_17.08.12.pdf RPA Report (2005): Environmental Risk Reduction Strategy and Analysis of Advantages and Drawbacks for Hexavalent Chromium – Under Framework Contract: CPEC 24. Final Report prepared for the Department for Environment, Food and Rural Affairs. Risk & Policy Analysts Limited, Norfolk, UK.
92 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Steele, L.S. and Brandewie, B. (2007): Treated Aluminium Article and method for making same. EP Patent 1780313 A2.
TURI - Toxics Use Reduction Institute (2006): Five chemicals alternative assessment study, University of Massachusetts Lowell.
Vasques, M.J., Halada, G.P., Clayton, C.R and Longtin, J.P. (2002): On the nature of the chromate conversion coating formed on intermetallic constituents of AA2024-T3. Surface and Interface Analysis 33: 607-616.
Wang, D. & Bierwagen, G., 2009: Sol-gel coatings on metals for corrosion protection, Progress in Organic Coatings, 64, pages 327-338.
Zhao, J., Xia, L., Sehgal, A., Lu, D., McCreery, R.L. and Frankel, G.S. (2001): Effects of chromate and chromate conversion coatings on corrosion of aluminium alloy 2024-T3. Surface and Coatings Technology 140: 51-57.
93 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
APPENDIX 1 – INITIAL LIST OF POTENTIAL ALTERNATIVES TO CHROMIUM TRIOXIDE-CONTAINING SURFACE TREATMENTS
ID Alternative Category Reason for Screening out
1 Acidic surface treatments 1
2 (Summarised under 2 Iridite NCP (Al, F, Oxygen) Zr/Ti-based treatments)
3 Manganese-based treatments 1
This is no alternative for surfaces treatment Mineral Tie-Coat (cathodic 4 3 discussed within this dossier--> Process is mineralisation) related to functional chrome applications. 5 Molybdate based coatings 2 This is no alternative for surfaces treatment 6 Plasma electrolytic oxidation 3 discussed within this dossier--> Process is related to functional chrome applications. This is no alternative for surfaces treatment 7 Polymer coatings 3 discussed within this dossier --> Process is related to primer applications. Adhesion and corrosion protection poor on Self-Assembling molecule relevant Al alloys, not seen as general 8 3 systems alternative for surfaces treatment discussed within this dossier. 9 Silane/Siloxane (organometallics) 1 10 Sol-gel coatings 1 This process is only applicable on Mg and its Tagnite (inorganic Silica or 11 3 alloys, no general alternative for surfaces vanadate) treatment discussed within this dossier. 12 Cr(III)-based processes 1 13 Zr/Ti-based coatings 1 1 (summarized under Vapor deposition based 14 LTS with technologies Silane/siloxane Benzotriazole or 5-methyl-1H- 15 2 benzotriazole This is no alternative for surfaces treatment 16 Hot water sealing 3 discussed within this dossier. 17 PVD 2 18 Other oxide-based coatings 1 19 Low tin steel 1 1(summarized under 20 Tannic acid acidic surface treatments) Non-chrome deoxidiser solution 21 1 based on Mineral acids or Iron 22 Formic acid 3 Stripping of organic coatings:
94 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
ID Alternative Category Reason for Screening out
-- Not suitable for assemblies with dissimilar metals Not allowed for the use with high strength steels Hydrogen peroxide activated 23 1 benzyl alcohol with acid
95 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
APPENDIX 2 – GENERAL INFORMATION AND THE RISK FOR HUMAN HEALTH AND THE ENVIRONMENT FOR RELEVANT SUBSTANCES
APPENDIX 2.1: MAIN PROCESSES AND POST-TREATMENTS APPENDIX 2.1.1: ALTERNATIVE 1: Acidic surface treatments Table 1: Substance IDs and properties.
Physico- Parameter Value chemical Value properties Physical state at Chemical name and Sulphuric acid (mono constituent substance) 20°C and 101.3 Liquid (odourless) composition kPa 10.4-10.5°C EC number 231-639-5 Melting point (for pure sulfuric acid) 1.83 g/cm3 (20°C, for CAS number 7664-93-9 Density 100%) IUPAC name Sulfuric acid Vapour pressure 0.49 hPa (20°C)
Molecular formula H2SO4 Water solubility Miscible with water Molecular weight 98.08 g/mol Flammability Non flammable Physicochemical Parameter Value Value properties Physical state at Chemical name and Tannic acid 20°C and 101.3 Solid composition kPa EC number 215-753-2 Melting point 218 °C CAS number 1401-55-4 Density 0.44 g/cm³ (20 °C) 2,3-dihydroxy-5-({[(2R,3R,4S,5R,6R)-3,4,5,6- tetrakis({3,4-dihydroxy-5-[(3,4,5- IUPAC name Vapour pressure - trihydroxyphenyl)carbonyloxy]phenyl}carbonyloxy)oxan- 2-yl]methoxy}carbonyl)phenyl 3,4,5-trihydroxybenzoate
Molecular formula C76H52O46 Water solubility 250 g/L (20 °C) Flammability - Molecular weight 1701.2 g/mol Flash point 199 °C
Table 2: Classification and labelling of relevant substances.
Hazard Class Hazard Statement Number Additional Regulatory and CLP Substance Name and Category Code(s) of classification and status Code(s) (labelling) Notifiers labelling comments Specific Concentration limits: H314 (Causes severe REACH registered; Skin Corr. 1A: C ≥ Sulphuric acid skin burns and eye Skin Corr. 1A 15%, H314 Included in CLP (CAS 7664-93-9) damage) n/a Regulation, Annex VI Met. Corr. 1 Skin Irrit. 2: 5% ≤ C < H290 (May be (index number 016-020- (EC 231-639-5) 15%, H315 corrosive to metals) 00-8); Eye Irrit. 2: 5% ≤ C < 15%; H319 H319 (Causes serious Tannic acid Eye Irrit. 2 750 Not REACH registered; eye irritation)
96 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Class Hazard Statement Number Additional Regulatory and CLP Substance Name and Category Code(s) of classification and status Code(s) (labelling) Notifiers labelling comments (CAS 1401-55-4) H412 (Harmful to Not included in CLP Aquatic (EC 215-753-2) aquatic life with long 322 Regulation, Annex VI; Chronic 3 lasting effects) Included in C&L inventory 33 additional notifiers submitted a H315 (Causes skin classification as Skin Skin Irrit. 2 33 irritation) Irrit. 2, in combination with Eye Irrit. 2 and Aquatic Chronic 3
APPENDIX 2.1.2: ALTERNATIVE 2: Cr(III)-based surface treatments Table 1: Substance ID and physicochemical properties
Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C and Chromium(III) sulphate Solid composition 101.3 kPa EC number 233-253-2 Melting point 90 °C CAS number 10101-53-8 Density 3.10 g/cm³ (anhydrous) IUPAC name Chromium(III) sulphate Vapour pressure - Insoluble in water and acids Molecular formula Cr2(SO4)3 Water solubility (anhydrous). Soluble as hydrate Flammability Non-flammable Molecular weight 392.18 g/mol Flash point: - Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C and Chromium(III) chloride solid composition 101.3 kPa EC number 233-038-3 Melting point ca. 1150 °C CAS number 10025-73-7 Density 2.87 g/cm³ (25 °C) IUPAC name Chromium(III) chloride Vapour pressure -
Molecular formula CrCl3 Water solubility 0.585 g/cm³ Flammability Non-flammable Molecular weight 158.36 g/mol Flash Point -
Table 2: Hazard classification and labelling overview
Hazard Hazard Class Number Additional Statement Regulatory and CLP Substance Name and Category of classification and Code(s) status Code(s) Notifiers labelling comments (labelling) Currently not REACH Chromium registered; sulphate 1,103 notifiers did not Not included in the CLP (CAS 10101-53- Not classified - 1103 classify the substance. Regulation, Annex VI; 8) Included in C&L inventory (EC 233-253-2)
97 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Class Number Additional Statement Regulatory and CLP Substance Name and Category of classification and Code(s) status Code(s) Notifiers labelling comments (labelling) H302 (Harmful Acute Tox. 4 Additional 6 parties if swallowed) notified the substance as Currently not REACH Chromium H315 (Causes Acute Tox 4 (H302) Skin Irrit. 2 registered; chloride skin irritation) only. Further 6 notifiers Not included in the CLP (CAS 10025-73- H319 (Causes 41 Regulation, Annex VI; 7) submitted the Eye Irrit. 2 serious eye classification as Acute Included in C&L inventory (EC 233-038-3) irritation) Tox 4 (H302) and H330 (Fatal if Aquatic Chronic 3 Acute Tox. 1 inhaled) (H412).
APPENDIX 2.1.3: ALTERNATIVE 3: Silane/Siloxane and sol-gel coatings Table 1: Substance IDs and properties
Parameter Value Physicochemical properties Value
Chemical name and Methyl trimethoxysilane Physical state at 20°C and liquid composition (MTMS) 101.3 kPa EC number 214-685-0 Melting point < -77 °C CAS number 1185-55-3 Density 0.96 g/cm³ (20°C) IUPAC name trimethoxy(methyl)silane Vapour pressure 7.84 hPa (20°C)
Molecular formula C4H12O3Si Water solubility 29 g/L (20°C) Flammability flammable Molecular weight 136.05 g/mol Flash point 11.5 °C (1013 hPa)
Parameter Value Physicochemical properties Value Chemical name and Vinyl trimethoxysilane Physical state at 20°C and liquid composition (VTMS) 101.3 kPa EC number 220-449-8 Melting point -97 °C CAS number 2768-02-7 Density 0.97 g/cm³ (20 °C) IUPAC name Ethenyl(trimethoxy)silane Vapour pressure 920 Pa (20 °C)
Molecular formula C5H12O3Si Water solubility 9.4 g/L (20 °C, pH = 7) Flammability Flammable Molecular weight 148.05 g/mol Flash point 24 °C
Table 2: Hazard classification and labelling
Hazard Class Hazard Statement Additional Substance Number of Regulatory and CLP and Category Code(s) classification and Name Notifiers status Code(s) (labelling) labelling comments H225 (Highly Classification of Best Case: Flam. Liq. 2 flammable liquid and REACH registration ; vapour) notified to the C&L Methyl REACH registered; trimethoxysila 96 inventory by 96 parties. Not included in the CLP ne (MTMS) H317 (May cause an Further 93 parties Skin Sens. 1 Regulation, Annex VI; (CAS 1185- allergic skin reaction) classified the substance 55-3) as Flam. Liq. 2 only Information from C&L inventory (EC 214-685- H225 (Highly Instead of Flam. Liquid 0) Flam. Liq. 2 flammable liquid and 296 2 and Skin Sens. 1, 296 vapour) notifiers submitted the
98 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Class Hazard Statement Additional Substance Number of Regulatory and CLP and Category Code(s) classification and Name Notifiers status Code(s) (labelling) labelling comments H315 (Causes skin classification as Skin Irrit. 2 irritation) specified on the left to the C&L inventory. H319 (Causes serious Eye Irrit. 2 eye irritation) 64 additional notifiers submitted the same classification but H335 (May cause STOT SE 3 abstained from the respiratory irritation) classification as STOT SE 3. H225 (Highly Flam. Liq. 2 flammable liquid and vapour) H226 (Flammable Flam. Liq. 3 liquid and vapour) One or several classification as H315 (Causes skin Skin Irrit. 2 specified on the left irritation) 62 were notified to the H319 (Causes serious C&L inventory by Eye Irrit. 2 eye irritation) another 62 parties in total. H302 (Harmful if Acute Tox. 4 swallowed) H332 (Harmful if Acute Tox. 4 inhaled) H226 (Flammable Flam. Liq. 3 liquid and vapour) Classification included 176 REACH registered; H332 (Harmful if in REACH registration. Acute Tox. 4 Not included in the CLP inhaled) Regulation, Annex VI; 352 notifiers submitted Information from C&L H318 (Causes serious Eye Dam. 1 352 the classification as Eye inventory; eye damage) Dam. 1 only. Worst Case: H315 (Causes skin Included in the CoRAP Vinyl Skin Irrit. 2 irritation) list of substances: trimethoxysila ne (VTMS) H319 (Causes serious - Initial grounds of Eye Irrit. 2 concern: Human (CAS 2768- eye irritation) Additional health/Suspected 02-7) classifications included H335 (May cause Total sensitiser; STOT SE 3 in the C&L inventory (EC 220-449- respiratory irritation) number of Exposure/Wide by notifiers in different 8) additional dispersive use; H304 (May be fatal if combinations. notifiers: Worker exposure; Asp. Tox 1 swallowed and enters 32 notifiers sumitted the Exposure of sensitive 240 airways) classification as Muta. population; High H340 (May cause 1B and Carc. 1B. RCR; Aggregated Muta. 1B genetic effects) tonnage - Status: ongoing H350 (May cause Carc. 1B cancer)
99 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
APPENDIX 2.1.4: ALTERNATIVE 4: Manganese-based processes Table 1: Substance ID and physicochemical properties
Physico-chemical Parameter Value Value properties Potassium permanganate Chemical name and Physical state at 20°C and (mono constituent Solid (dark-purple or bronze-like) composition 101.3 kPa substance) EC number 231-760-3 Melting point Decomposes <240°C CAS number 7722-64-7 Density 2.7 g/cm3 (20°C) potassium IUPAC name Vapour pressure - oxido(trioxo)manganese
Molecular formula KMnO4 Water solubility ≥64 g/L (20°C)
Flammability Non flammable but will accelerate the burning of combustible Molecular weight 158.03 g/mol material. Flash point - Physico-chemical Parameter Value Value properties Aluminium Sulphate Chemical name and Physical state at 20°C and (mono constituent Solid (granules) composition 101.3 kPa substance) No Melting of substance EC number 233-135-0 Melting point (unspecified hydrate) was observed (25°C-550°C). 1.79 g/ cm3 (at 20°C, unspecified CAS number 10043-01-3 Density hydrate) IUPAC name Aluminium sulphate Vapour pressure -
Molecular formula Al2(SO4)3 Water solubility > 1000 g/L (20°C, pH = 2.4) Flammability Non flammable Molecular weight 342.15 g/mol Flash point - Physico-chemical Parameter Value Value properties Sodium dihydrogen- Chemical name and Physical state at 20°C and orthophosphate (mono Solid (granules) composition 101.3 kPa constituent substance) EC number 231-449-2 Melting point > 449°C CAS number 7558-80-7 Density 2.36 g/ cm3 (20.5°C) sodium dihydrogen IUPAC name Vapour pressure - phosphate 50.2-52 .0 %w/w Molecular formula NaH2PO4 Water solubility (20°C, pH = 3.6-4.0) Flammability Non flammable Molecular weight 119.98 g/mol Flash point -
100 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Table 2: Hazard classification and labelling overview
Hazard Hazard Number Additional Substance Class and Statement of classification and Regulatory and CLP status Name Category Code(s) Notifiers labelling comments Code(s) (labelling) H272 (May Ox. Sol. 2 intensify fire; oxidizer) H302 (Harmful if Acute Tox. 4 swallowed) Classification Potassium according CLP permanganate Aquatic H400 (Very toxic REACH registered; Acute 1 to aquatic life) Regulation Annex VI; KMnO4 n/a Included in CLP Regulation, Annex VI (index number 025- (CAS 7722-64-7) H410 (Very toxic 002-00-9); (EC 231-760-3) Aquatic to aquatic life Chronic 1 with long lasting effects) H314 (Causes Further classification Skin Corr. severe skin burns according to REACH 1C and eye damage) registration; H290 (May be Classification Met. Corr. 1 corrosive to included in REACH metals) joint registration and submitted by 131 131 notifiers to the C&L H318 (Causes inventory. Eye Dam. 1 serious eye 361 parties notified damage) the substance as Eye Dam. 1 only. Not - 49 classified H302 (Harmful if Acute Tox. 4 swallowed) H318 (Causes Eye Dam. 1 serious eye Aluminium damage) REACH registered; Sulphate Al2(SO4)3 H319 (Causes Not included in CLP Regulation, Annex VI; (CAS 10043-01- Eye Irrit. 2 serious eye 3) irritation) Information from C&L inventory (EC 233-135-0) H315 (Causes Skin Irrit. 2 skin irritation) Additional ~ 180 notifiers submitted H335 (May cause one or several of the ~180 STOT SE 3 respiratory additional irritation) classifications on the left to the C&L Aquatic H400 (Very toxic Acute 1 to aquatic life) H410 (Very toxic Aquatic to aquatic life Chronic 1 with long-lasting effects) H411 (Toxic to Aquatic aquatic life with Chronic 2 long-lasting effects) Not Sodium - 502 Information from REACH registered; dihydrogen- classified REACH registration;
101 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Number Additional Substance Class and Statement of classification and Regulatory and CLP status Name Category Code(s) Notifiers labelling comments Code(s) (labelling) orthophosphate notified to the C&L Not included in CLP NaH2PO4 inventory by 502 Regulation, Annex VI; (CAS 7558-80-7) parties (of which 51 Information from C&L did not classify due to inventory (CAS 231-449-2) lacking data). H315 (Causes Skin Irrit. 2 skin irritation) One or several H319 (Causes classification as Eye Irrit. 2 serious eye specified on the left 77 irritation) were notified to the C&L inventory by 77 H335 (May cause parties in total. STOT SE 3 respiratory irritation)
APPENDIX 2.1.5: ALTERNATIVE 5: Molybdates and Molybdenum based processes Table 1: Substance ID and properties
Physico-chemical Parameter Value Value properties Disodium molybdate Chemical name and Physical state at 20°C and (monoconstituent Solid (crystalline, odourless) composition 101.3 kPa substance) EC number 7631-95-0 Melting point 687.0°C (anhydrous Substance) CAS number 231-551-7 Density 2.59 g/cm3 disodium IUPAC name tetraoxomolybdate Vapour pressure - dihydrate
. Molecular formula Na2MoO4 2H2O Water solubility 654.2 g/L Flammability Molecular weight 241. 95 g/mol - Flash point Physico-chemical Parameter Value Value properties Orthophosphoric acid Chemical name and Physical state at 20°C and Solid (crystalline, if no water (mono constituent composition 101.3 kPa attached) substance) EC number 231-633-2 Melting point 41.1 °C (101 kPa) CAS number 7664-38-2 Density 1.84 g/cm3 (38°C) IUPAC name Phosphoric acid Vapour pressure 80 Pa (25°C, extrapolated)
Molecular formula H3O4P Water solubility 5480 g/ L (cold water, pH= 0.5) Flammability non flammable Molecular weight 98.0 g/mol Flash point - Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C and Cerium trifluoride Pale pink powder composition 101.3 kPa
102 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Physico-chemical Parameter Value Value properties EC number 231-841-3 Melting point 1430°C CAS number 7758-88-5 Density 6.157 g/cm³ IUPAC name cerium(3+) trifluoride Vapour pressure - ≤ 1.1 mg/L (20°C, pH= 4)
Molecular formula CeF3 Water solubility ≤ 0.27 mg/L (20°C, pH =7) ≤ 0.077 mg/L (20°C, pH= 9) Flammability Non flammable Molecular weight 197.1 g/mol Flash point -
Table 2: Hazard classification and labelling overview.
Hazard Class Hazard Statement Number Additional Regulatory and CLP Substance Name and Category Code(s) of classification and status Code(s) (labelling) Notifiers labelling comments
Not classified - 163 In line with the information submitted H315 (Causes skin with the REACH Skin Irrit. 2 irritation) registration 163 notifiers did not classify Sodium H319 (Causes the substance. molybdate Eye Irrit. 2 serious eye Additional 188 notifiers irritation) classified the substance (CAS 7631-95-0) 118 H332 (Harmful if with hazards (see on the (EC 231-551-7) Acute Tox. 4 inhaled) left). 93 notifiers mentioned H335 (May cause the single classification: STOT SE 3 respiratory Aquatic Chronic 3. irritation)
H412 (Harmful to Aquatic Chronic aquatic life with 93 3 long lasting effects) H314 (Causes Skin Corr. 1B severe skin burns n/a Legal classification. REACH registered; Phosphoric acid and eye damage) Included in CLP (CAS 7664-38-2) Regulation, Annex VI Additional self- (EC 231-633-2) H290 (May be (index number 015-011- Met. Corr. 1 n/a classification according corrosive to metals) 00-6); to REACH registration;
According to the H312 (Harmful in REACH Registration Acute Tox. 4 contact with skin) substance is not classified. Seven REACH registered; H315 (Causes skin Cerium fluoride Skin Irrit. 2 notifiers submitted this Not included in CLP irritation) (CAS 7758-88-5) information to the C&L Regulation, Annex VI; 25 inventory. (EC 231-841-3) H319 (Causes Included in C&L Eye Irrit. 2 serious eye inventory irritation) However, 25 parties H332 (Harmful if notified the substance Acute Tox. 4 inhaled) for various hazards (see
103 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Class Hazard Statement Number Additional Regulatory and CLP Substance Name and Category Code(s) of classification and status Code(s) (labelling) Notifiers labelling comments H335 (May cause classifications on the STOT SE 3 respiratory left). irritation)
APPENDIX 2.1.6: ALTERNATIVE 6: Organometallics (Zr- and Ti-based products) Table 1: Substance ID and properties. Physicochemical Parameter Value Value properties Chemical name and Physical state at 20°C and Hexafluorotitanic acid Liquid composition 101.3 kPa EC number 241-460-4 Melting point < 0°C CAS number 17439-11-1 Density 1.675 g/cm³ (25°C) IUPAC name Hexafluorotitanate(2-) Vapour pressure 23 hPa (20 °C)
Molecular formula H2F6Ti Water solubility Fully miscible Flammability - Molecular weight 163.87 g/mol Flash point - Physicochemical Parameter Value Value properties Chemical name and Physical state at 20°C and Hexafluorozirconic acid liquid composition 101.3 kPa EC number 234-666-0 Melting point - CAS number 12021-95-3 Density 1.512 g/cm³ (25 °C) IUPAC name Hexafluorozirconate(2-) Vapour pressure -
Molecular formula H2F6Zr Water solubility Fully miscible Flammability - Molecular weight 207.23 g/mol Flash point - Physicochemical Parameter Value Value properties Chemical name and Physical state at 20°C and Zirconium dioxide solid composition 101.3 kPa EC number 215-227-2 Melting point 2680 °C CAS number 1314-23-4 Density 5.77 g/cm³ (20 °C) IUPAC name Zirconium dioxide Vapour pressure -
Molecular formula ZrO2 Water solubility < 55 µg/L (20 °C, pH = 6.5) Flammability - Molecular weight 123.22 g/mol Flash point -
Table 2: Hazard classification and labelling overview.
Hazard Hazard Class Additional Substance Statement Number of Regulatory and CLP and Category classification and Name Code(s) Notifiers status Code(s) labelling comments (labelling) H290 (May be Fluorotitanic Met. Corr. 1 corrosive to 33 REACH registered; acid metals)
104 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Class Additional Substance Statement Number of Regulatory and CLP and Category classification and Name Code(s) Notifiers status Code(s) labelling comments (labelling) (CAS 17439-11- H301 (Toxic if Not included in the CLP Acute Tox. 3 1) swallowed) Regulation, Annex VI; (EC 241-460-4) Included in C&L H311 (Toxic in Acute Tox. 3 inventory contact with skin) Classification as included in REACH H331 (Toxic if Acute Tox. 3 registration. inhaled) H314 (Causes Skin Corr. 1B severe skin burns and eye damage) H300 (Fatal if Acute Tox. 2 swallowed) H310 (Fatal in Acute Tox. 2 contact with skin) H314 (Causes Additional 24 notifiers Skin Corr. 1B severe skin burns 24 listed other and eye damage) classification. H318 (Causes Eye Dam. 1 serious eye damage) H330 (Fatal if Acute Tox. 2 inhaled) Commercial Xn R20/21/22 product (Acute Tox. 4, Chrome-free oral, dermal Harmful by passivation for and inhalation) inhalation, in contact with skin aluminium and if swallowed. Contains 1-5% Source of information: Information from related n/a of CAS 12021- MSDS Iridite NCP MSDS 95-3 (EC 234- 666-0) Xi R36/38 (for (Skin Irrit. 2 Irritating to eyes classification of and skin. substance please Eye Irrit. 2) see below) H301 (Toxic if Acute Tox. 3 swallowed) H311 (Toxic in Acute Tox. 3 contact with skin) H314 (Causes 76 Fluorozirconic REACH registered; Skin Corr. 1B severe skin burns acid and eye damage) Not included in the CLP (CAS 12021-95- Regulation, Annex VI; H330 (Fatal if 3) Acute Tox. 2 Included in C&L inhaled) (EC 234-666-0) inventory H290 (May be Met. Corr. 1 corrosive to Further classification metals) - according to REACH H331 (Toxic if registration; Acute Tox. 3 inhaled)
Not classified - 750 REACH registered;
105 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Class Additional Substance Statement Number of Regulatory and CLP and Category classification and Name Code(s) Notifiers status Code(s) labelling comments (labelling) H315 (Causes Skin Irrit. 2 skin irritation) Zirconium 750 notifiers did not dioxide H319 (Causes classify the substance. Eye Irrit. 2 serious eye (CAS 1314-23- 73 Additional 73 notifiers irritation) 4) did mention human health hazards, see cells H335 (May cause (EC 215-227-2) on the left). STOT SE 3 respiratory irritation)
APPENDIX 2.1.7: ALTERNATIVE 7: Benzotriazole based processes, e.g. 5-methyl-1H- benzotriazol Table 1: Substance IDs and properties for relevant substances.
Physicochemical Parameter Value Value properties Chemical name and 5-methyl-1H- Physical state at 20°C solid composition benzotriazol and 101.3 kPa EC number 205-265-8 Melting point 80-82 °C CAS number 136-85-6 Density ca. 1.3 g/cm³ (predicted) IUPAC name 5-Methylbenzotriazole Vapour pressure -
Molecular formula C7H7N3 Water solubility 6.0 g/L (25 °C) Molecular weight 133.15 g/mol Flammability 210-212 °C
Table 2: Hazard classification and labelling
Hazard Additional Hazard Class Number Substance Statement classification and Regulatory and CLP and Category of Name Code(s) labelling status Code(s) Notifiers (labelling) comments Currently not REACH 36 notifiers notified registered; the substance with H302 (Harmful if the single hazard Not Included in CLP 5-methyl-1H- swallowed) Acute Tox. 4. Regulation, Annex Acute Tox. 4 36 VI; Included in the benzotriazol C&L Inventory (6- methylbenzo-
triazole) (CAS 136-85- H302 (Harmful if Acute Tox. 4 Additional 23 6) swallowed) notifiers classified (EC 205-265-8) H315 (Causes the substance both Skin Irrit. 2 Included in the C&L skin irritation) 23 with Acute Tox. 4 Inventory H319 (Causes and with three Eye Irrit. 2 serious eye additional hazards irritation) (see left).
106 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Additional Hazard Class Number Substance Statement classification and Regulatory and CLP and Category of Name Code(s) labelling status Code(s) Notifiers (labelling) comments H335 (May cause STOT SE 3 respiratory irritation)
APPENDIX 2.1.8: ALTERNATIVE 8: PVD Table 1: Substance ID and properties for an exemplary tungsten carbide-cobalt coating.
Parameter Value Physicochemical properties Value
Chemical name and Titanium nitride (mono Physical state at 20°C and Solid (gold) composition constituent substance) 101.3 kPa EC number 247-117-5 Melting point 2930°C CAS number 25583-20-4 Density 5.22 g/cm3 IUPAC name Titanium nitride Vapour pressure -
Molecular formula TiN Water solubility Insoluble in Water
Flammability Non flammable Molecular weight 61.87 g/mol Flash Point: -
Parameter Value Physicochemical properties Value
Chemical name and Titanium carbide (mono Physical state at 20°C and Solid (crystalline) composition constituent substance) 101.3 kPa EC number 235-120-4 Melting point 3067°C CAS number 12070-08-5 Density 4.93 g/cm3 IUPAC name Titanium carbide Vapour pressure -
Molecular formula TiC Water solubility Insoluble (< 0.1 mg/L)
Flammability Non flammable Molecular weight 59.88 g/mol Flash point -
Parameter Value Physicochemical properties Value
Chemical name and Physical state at 20°C and Zirconium nitride Solid (yellow to brown) composition 101.3 kPa EC number 247-166-2 Melting point 2980°C CAS number 25658-42-8 Density 7.09 g/cm³ (at 25°C) IUPAC name Zirconium nitride Vapour pressure -
Molecular formula ZrN Water solubility Insoluble
Flammability Highly flammable Molecular weight 105.23 g/mol Flash point -
Parameter Value Physicochemical properties Value
Chemical name and Silicon carbide (mono Physical state at 20°C and Solid composition constituent substance) 101.3 kPa
107 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Parameter Value Physicochemical properties Value
Dissociates into graphite and EC number 206-991-8 Melting point silicon at 2700°C CAS number 409-21-2 Density 3.22 g/cm³ (at 25°C) IUPAC name Silicon carbide Vapour pressure -
Molecular formula CSi Water solubility Insoluble < 0.1 mg/L
Flammability Non flammable Molecular weight 40.1 g/mol Flash point: -
Table 2: Hazard classification and labelling overview.
Additional Hazard Class Hazard Statement Number classification Regulatory and CLP Substance Name and Category Code(s) of and labelling status Code(s) Notifiers (labelling) comments
Titanium Carbide Not classified 18 (CAS 12070-08-5) Notified classification H 228 (flammable (EC 235-120-4) Flam. Sol 1 Solid)
Not classified 11
Titanium nitride H 228 (flammable Solid) (CAS 25583-20-4 ) Flam. Sol. 2 Notified Classification H 315 (causes skin (EC 247-117-5) Skin Irrit. 2 10 irritation) Eye Irrit. 2 H 319 (causes serious eye irritation) H315 (causes skin irritation) Zirconium nitride Skin Irrit. 2 H319 (causes serious (CAS 25658-42-8) Eye Irrit. 2 1 Notified classification eye irritation) (EC 247-166-2) STOT SE 3 H335 may cause respiratory irritation)
Not classified - 604
H350 (may cause Carc. 1B cancer) 50 Silicon carbide STOT RE 1 H372 (causes damage to organs) (CAS 409-21-2) (EC 206-991-8) H315 (causes skin irritation) Skin Irrit. 2 H319 (causes serious Eye Irrit. 2 25 eye irritation) STOT SE 3 H335 (may cause respiratory irritation)
108 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
APPENDIX 2.1.9: ALTERNATIVE 9: Other oxide based coatings The composition of the alternative is confidential business information.
APPENDIX 2.1.10: ALTERNATIVE 10: Low tin steel (LTS) Table 1: Substance IDs and properties of relevant substances.
Parameter Value Physicochemical properties Value Chemical name and Physical state at Tetraethyl orthosilicate liquid composition 20°C and 101.3 kPa EC number 201-083-8 Melting point -82 °C CAS number 78-10-4 Density 0.94 g/cm³ (20°C) IUPAC name Tetraethoxysilane Vapour pressure 110 Pa (20°C)
Molecular formula C8H20O4Si Water solubility 1.49 g/L (23°C, pH = 7) Flammability - Molecular weight 208.12 g/mol Flash point 45°C (1013 hPa)
Parameter Value Physicochemical properties Value
Chemical name and Physical state at hexamethyl-disiloxane Liquid (colourless) composition 20°C and 101.3 kPa EC number 203-492-7 Melting point -68.2°C CAS number 107-46-0 Density 0,76 g/cm³ IUPAC name hexamethyldisiloxane Vapour pressure 43.0 hPa at 20°C Slightly soluble (0.1- Molecular formula C6H18O2Si2 Water solubility 100 mg/L) Flammability Gas: Lower explosion limit 1.5 %; Upper Molecular weight 162.38 g/mol explosion limit 14.65%
Flash point -6°C Table 2: Hazard classification and labelling overview. Additional Hazard Statement Number Substance Hazard Class and classification and Regulatory and Code(s) of Name Category Code(s) labelling CLP status (labelling) Notifiers comments
H226 (Fammable REACH Tetraethyl liquid and vapour) registered; orthosilicate Flam. Liq. 3 H332 (Harmful if Included in the (TEOS) Acute Tox. 4 * inhaled) CLP Regulation, (CAS 78-10- n/a - Eye Irrit. 2 H319 (Causes serious Annex VI (index 4) STOT SE 3 eye irritation) number: 014-005- (EC 201- 00-0) 083-8) H335 (May cause respiratory irritation)
109 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Additional Hazard Statement Number Substance Hazard Class and classification and Regulatory and Code(s) of Name Category Code(s) labelling CLP status (labelling) Notifiers comments H225 (highly flammable liquid and REACH hexamethyl- vapour) disiloxane Flam. Liq. 2 registered; H400(very toxic to notified (CAS 107- Aquatic Acute 1 296 aquatic life) - classification and 46-0) Aquatic Chronic 1 H410 (very toxic to labelling (EC 203- aquatic life with long according to CLP 492-7) lasting effects) criteria. Not classified 99
APPENDIX 2.2: PRE-TREATMENTS APPENDIX 2.2.1: Inorganic acids and additives Table 1: Substance IDs and physicochemical properties are presented (not exhaustive): Physico-chemical Parameter Value Value properties Chemical name and Sulphuric acid (mono Physical state at 20°C Liquid (odourless) composition constituent substance) and 101.3 kPa 10.4-10.5°C EC number 231-639-5 Melting point (pure sulfuric acid) 1.83 g/cm3 (20°C, pure CAS number 7664-93-9 Density sulphuric acid) IUPAC name Sulfuric acid Vapour pressure 0.49 hPa (20°C)
Molecular formula H2SO4 Water solubility Miscible with water Flammability Non flammable Molecular weight 98.08 g/mol Flash point - Physico-chemical Parameter Value Value properties Orthophosphoric acid Chemical name and Physical state at 20°C Solid (crystalline, if no water (mono constituent composition and 101.3 kPa attached) substance) EC number 231-633-2 Melting/freezing point 41.1 °C (101 kPa) CAS number 7664-38-2 Density 1.84 g/cm3 (38°C) IUPAC name Phosphoric acid Vapour pressure 80 Pa (25°C, extrapolated)
Molecular formula H3PO4 Water solubility 5480g/ L (cold water, pH= 0.5) Flammability Non flammable Molecular weight 98.00 g/mol Flash point - Physico-chemical Parameter Value Value properties Chemical name and Nitric acid (mono Physical state at 20°C Liquid (fumes in moist air) composition constituent substance) and 101.3 kPa EC number 231-714-2 Melting/freezing point - 41.60 °C CAS number 7697-37-2 Density 1.51 g/cm3 (20°C)
110 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Physico-chemical Parameter Value Value properties IUPAC name Nitric acid Vapor pressure 9.00 kPa (25°C)
Molecular formula HNO3 Surface Tension - Molecular weight 63.01 g/mol Water solubility > 1000g /L (20°C, pH= -1) Flammability Non flammable Molecular structure Flash point - Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C Chromium(III) sulphate Solid composition and 101.3 kPa EC number 233-253-2 Melting point 90 °C CAS number 10101-53-8 Density 3.10 g/cm³ (anhydrous) IUPAC name Chromium(III) sulphate Vapour pressure - Insoluble (anhydrous). Soluble Molecular formula Cr2(SO4)3 Water solubility as hydrate. Flammability Non-flammable Molecular weight 392.18 g/mol Flash point - Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C Iron(II)-sulphate Solid composition and 101.3 kPa EC number 231-753-5 Melting point > 300°C (decomposes) CAS number 7720-78-7 Density 3.65 g/cm³ IUPAC name Iron(2+) sulfate Vapour pressure -
Molecular formula FeSO4 Water solubility Very soluble (>10000 mg/L) Flammability Non flammable Molecular weight 151.9 g/mol Flash point - Physico-chemical Parameter Value Value properties Chemical name and Nitric acid (mono Physical state at 20°C Liquid (fumes in moist air) composition constituent substance) and 101.3 kPa
EC number 231-714-2 Melting point - 41.60 °C
CAS number 7697-37-2 Density 1.51 g/cm3 (20°C)
IUPAC name Nitric acid Vapour pressure 9.00 kPa (25°C)
Molecular formula HNO3 Water solubility > 1000g /L (20°C, pH= -1)
Flammability non flammable Molecular weight 63.01 g/mol Flash point - Physicochemical Parameter Value Value properties Chemical name and Physical state at 20°C Hydrogenperoxide Liquid (odourless, colourless) composition and 101.3 kPa
111 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Physico-chemical Parameter Value Value properties 0.43°C (1013 hPa, for pure EC number 231-765-0 Melting point hydrogen peroxide) 1.44 g/cm3 (calculated for pure CAS number 7722-84-1 Density hydrogen peroxide at 25°C) 2.99 hPa (calculated for pure IUPAC name Hydrogen peroxide Vapour pressure hydrogen peroxide at 25°C) miscible in water in all Molecular formula H2O2 Water solubility proportions Flammability - Molecular weight 34.01 g/mol Flash point: - Physicochemical Parameter Value Value properties Chemical name and Benzyl alcohol Physical state at 20°C liquid composition and 101.3 kPa
EC number 202-859-9 Melting point - 15.4°C
CAS number 100-51-6 Density 1.04 g/cm3 (22°C)
IUPAC name phenylmethanol Vapour pressure 7 Pa (20°C)
Molecular formula C7H8O Water solubility 44.0 g/L (50°C)
Not considered to be highly Flammability Molecular weight 108.14 g/mol flammable Flash Point - Physicochemical Parameter Value Value properties
Table 2: Hazard classification and labelling overview Hazard Hazard Statement Number Additional Substance Class and Regulatory and Code(s) of classification and Name Category CLP status Notifiers labelling comments Code(s) (labelling) Specific Concentration H314 (Causes severe limits: skin burns and eye REACH registered; Sulphuric acid damage) Skin Corr. 1A: C ≥ 15%, (CAS 7664-93- Skin Corr. 1A H314 Included in CLP H290 (may be n/a Regulation, Annex VI 9) Met. Corr. 1 Skin Irrit. 2: 5% ≤ C < corrosive to metals) (index number 016- 15%, H315 (EC 231-639-5) 020-00-8); Eye Irrit. 2: 5% ≤ C <
15%; H319 H314 (Causes severe Phosphoric acid Skin Corr. 1B skin burns and eye n/a Legal classification. REACH registered; (CAS 7664-38- damage) Included in CLP Regulation, Annex VI 2) Additional self- H290 (May be (index number 015- (EC 231-633-2) Met. Corr. 1 n/a classification according corrosive to metals) 011-00-6); to REACH registration;
112 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Statement Number Additional Substance Class and Regulatory and Code(s) of classification and Name Category CLP status Notifiers labelling comments Code(s) (labelling) H272 (May intensify Ox. Liq. 3 fire; oxidizer) H314 (Causes severe Skin Corr. 1A skin burns and eye n/a damage) Additional classification H290 (May be Met. Corr. 1 according to REACH REACH registered; Nitric acid corrosive to metals) registration. (CAS 7697-37- Included in CLP 2) Classification notified to Regulation, Annex VI Not classified - 257 the C&L inventory. (index number 007- (EC 231-714-2) 004-00-1) H315 (Causes skin Skin Irrit. 2 irritation) Classification notified to the C&L inventory. H318 (Causes serious Eye Dam. 1 271 eye damage) Further 163 notifiers classified the substance as H335 (May cause Eye Dam. 1 only. STOT SE 3 respiratory irritation) Currently not REACH Chromium registered; sulphate Not included in the 1103 notifiers did not (CAS 10101-53- Not classified - 1103 CLP Regulation, classify the substance. 8) Annex VI; (EC 233-253-2) Included in C&L inventory Reach registered Iron(II) sulphate H302 (harmful if substance; Harmonised swallowed) classification- Annex (CAS 7720-78- Acute Tox. 4 H315 (causes skin VI of Regulation (EC) 7) Skin Irrit. 2 - irritation) No 1272/2008 (CLP (EC 231-753-5) Eye Irrit. 2 H319 (causes serious Regulation). eye irritation) (Index number: 026- 003-00-7) H272 (May intensify Nitric acid Ox. Liq. 3 REACH registered; fire; oxidizer) (CAS 7697-37- Included in CLP n/a 2) H314 (Causes severe Regulation, Annex VI Skin Corr. 1A skin burns and eye (index number 007- (EC 231-714-2) damage) 004-00-1)
REACH registered; H271 (May cause fire Included in CLP Ox. Liqu.1 or explosion; strong Regulation, Annex VI oxidiser) (index number 008- 003-00-9)
Hydrogen H302 (Harmful if Acute Tox. 4 550 Liquid peroxide swallowed) (CAS 7722- H314 (causes severe 84-1) Skin Corr. 1A skin burns and eye (EC 231-765-0) damage)
H332 (Harmful if Acute Tox 4. inhaled) H271 (May cause fire Ox. Liqu.1 or explosion; strong 352 oxidiser)
113 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Hazard Hazard Statement Number Additional Substance Class and Regulatory and Code(s) of classification and Name Category CLP status Notifiers labelling comments Code(s) (labelling) H302 (Harmful if Acute Tox. 4 swallowed) H314 (causes severe Skin Corr. 1A skin burns and eye damage) H318 (causes serious Eye Dam.1 eye damage) H332 (Harmful if Acute Tox 4. inhaled) H335 (may cause STOT SE 3 respiratory irritation)
H302 (Harmful if Acute Tox. 4 swallowed)
2502
H332 (Harmful if Acute Tox. 4 inhaled) REACH registered; Benzyl alcohol Included in CLP H302 (Harmful if (CAS 100-51-6) Acute Tox. 4 Regulation, Annex VI swallowed) (EC 202-859-9) (index number 603- 057-00-5 ) H312 (Harmful in Acute Tox 4 contact with skin.) 352 H318 (Causes serious Eye Dam.1 eye damage)
H332 (Harmful if Acute Tox. 4 inhaled)
Sulphuric acid H314 (Causes severe REACH registered; Skin Corr. 1A skin burns and eye (CAS 7664-93- Included in CLP damage) n/a 9) Regulation, Annex VI Met Corr. 1 H290 (may be (index number 016- (EC 231-639-5) corrosive to metal) 020-00-8);
APPENDIX 2.2.2: Pickling/Etching of copper Table 1: Substance IDs and properties for diammonium peroxodisulphate:
Physicochemical Parameter Value Value properties Chemical name and Diammonium Physical state at 20°C solid composition peroxodisulphate and 101.3 kPa EC number 231-786-5 Melting point 120 °C (decomposition) CAS number 7727-54-0 Density 1.26g/cm³ Diammonium IUPAC name Vapour pressure 1.96E-21 Pa peroxodisulphate Molecular formula H3N.1/2H2O8S2 Water solubility 850 g/L (25°C)
114 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
Molecular weight 228,20 g·mol−1 Flammability Non flammable Physicochemical Parameter Value Value properties Chemical name and Physical state at 20°C Ammonium chloride solid composition and 101.3 kPa EC number 235-186-4 Melting point 338 °C (decomposition) CAS number 12125-02-9 Density 1.53g/cm³ IUPAC name Ammonium chloride Vapour pressure 1,3 hPa (160,4 °C) Molecular formula ClH4N Water solubility 372 g/L (20°C) Molecular weight 53,49 g·mol−1 Flammability Non flammable
Table 2: Hazard classification and labelling
Hazard Additional Hazard Class Number Substance Statement classification and Regulatory and CLP and Category of Name Code(s) labelling status Code(s) Notifiers (labelling) comments H272 May Ox. Sol. 3 intensify fire; oxidizer H302 (Harmful if Acute Tox. 4 swallowed) H315 (Causes skin Skin Irrit. 2 irritations) Skin Sens. 1 H317 Diammonium H319 (Causes Harmonized peroxodisulphat Eye Irrit. 2 serious eye classification e irritation) H334 (may cause allergy or asthma symptoms or Resp. Sens. 1 breathing difficulties if inhaled) H335 (May cause STOT SE 3 respiratory irritation) H302 (Harmful if Acute Tox. 4 swallowed) Ammonium Harmonized chloride H319 (Causes classification Eye Irrit. 2 serious eye irritation)
115 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed. ANALYSIS OF ALTERNATIVES
APPENDIX 2.3: SOURCES OF INFORMATION Information on substance identities, physicochemical properties, hazard classification and labelling are based on online data searches. All online sources were accessed between June and September 2014. The main sources are:
1. European Chemicals Agency: http://echa.europa.eu/de/
2. ChemSpider internet site: http://www.chemspider.com
3. Sigma Aldrich Material Safety Data Sheet: http://www.sigmaaldrich.com
4. Chemical Book internet site: http://www.chemicalbook.com
5. Santa Cruz Biotechnology internet site: http://www.scbt.com/
6. PubChem internet site: http://pubchem.ncbi.nlm.nih.gov
7. ChemBlink internet site: http://www.chemblink.com/
8. Espimetals.com internet site: http://www.espimetals.com .
116 Use number: 5 Copy right protected - Property of Members of the CTAC Submission Consortium - No copying / use allowed.