DOCSLIB.ORG

Chapter 17: Corrosion and Degradation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

CHAPTER 17: CORROSION AND DEGRADATION ISSUES TO ADDRESS... • Why does corrosion occur ? • What metals are most likely to corrode? • How do temperature and environment affect corrosion rate? • How do we suppress corrosion? Chapter 17 - 1 THE COST OF CORROSION • Corrosion : -- the destructive electrochemical attack of a material. -- Al Capone's ship, Sapona, off the coast of Bimini. • Cost: Photos courtesy L.M. Maestas, Sandia National Labs. Used with permission. -- 4 to 5% of the Gross National Product (GNP)* -- this amounts to just over $400 billion/yr** Leaking battery Chapter 17 - 2 Electrochemical Considerations • Oxidation (anodic reaction) M Mn+ + ne - metal atoms lose or give up electrons • Reduction (Cathodic reaction) Mn+ + ne - M Mn+ + e - M(n-1)- metal ions gain electrons Chapter 17 - 3 CORROSION OF ZINC IN ACID • Two reactions are necessary: 2+ − -- oxidation reaction: Zn → Zn + 2e + − -- reduction reaction: + → 2H 2e H2(gas) H+ Oxidation reaction 2+ Zn Zn H+ + Acid Zinc flow of e - H 2e - H+ solution in the metal H+ H+ Adapted from Fig. 17.1, Callister 7e . H2(gas) (Fig. 17.1 is from M.G. Fontana, H+ Corrosion Engineering , 3rd ed., reduction reaction McGraw-Hill Book Company, 1986.) • Other reduction reactions: -- in an acid solution -- in a neutral or base solution + − − − O + 4H + 4e → 2H O O + 2H O + 4e → 4(OH) 2 2 2 2 Chapter 17 - 4 Not all metallic materials oxidize to form ions with the same degree of ease. Chapter 17 - 5 Galvanic couple: two metals eclectically connected in a liquid electrolyte wherein one metal becomes an anode and corrodes, while the other acts as a cathode. Chapter 17 - 6 The magnitude of such a voltage is the driving force for the electrochemical oxidation-reduction reaction. Chapter 17 - 7 STANDARD HYDROGEN (EMF) TEST electromotive force • Two outcomes: -- Metal sample mass -- Metal sample mass e- e- e- e- H (gas ) + - ne - 2 2e - ne - H 2e H+ n+ n+ M H+ M ions ions H+ Platinum Platinum metal, M metal, metal, M metal, 25°C 25°C 1M M n+ sol’n 1M H + sol’n 1M M n+ sol’n 1M H + sol’n --Metal is the anode (-) --Metal is the cathode (+) o < o > Vmetal 0 (relative to Pt) Vmetal 0 (relative to Pt) Adapted from Fig. 17.2, Callister 7e . Standard Electrode Potential Chapter 17 - 8 STANDARD EMF SERIES • EMF series • Metal with smaller V o o metal metal Vmetal corrodes. Au +1.420 V • Ex: Cd-Ni cell Cu +0.340 Pb - 0.126 - + Sn - 0.136 Ni - 0.250 o Co - 0.277 ∆V = more cathodic Cd - 0.403 0.153V Cd 25°C Ni Fe - 0.440 Cr - 0.744 Zn - 0.763 1.0 M 1.0 M Al - 1.662 Cd 2+ solution Ni 2+ solution Mg - 2.363 more anodic Na - 2.714 Data based on Table 17.1, Adapted from Fig. 17.2, Callister 7e . K - 2.924 Callister 7e . Chapter 17 - 9 CORROSION IN A GRAPEFRUIT Cathode Anode + - Cu H+ Zn H+ Zn 2+ reduction 2e - oxidation + + − → 2H 2e H2(gas) H+ + + + − → + O 2 4H 4e 2H2O H Acid H+ H+ H+ Chapter 17 -10 EFFECT OF SOLUTION CONCENTRATION • Ex: Cd-Ni cell with • Ex: Cd-Ni cell with standard 1 M solutions non-standard solutions o − o = − = o − o − RT X VNi VCd 0.153 VNi VCd VNi VCd ln - + - + nF Y n = #e - per unit oxid/red Cd 25°C Ni Cd T Ni reaction (= 2 here) F = 1.0 M 1.0 M X M Y M Faraday's Cd 2+ solution Ni 2+ solution Cd 2+ solution Ni 2+ solution constant = 96,500 • Reduce VNi - VCd by C/mol. --increasing X --decreasing Y Chapter 17 -11 GALVANIC SERIES • Ranks the reactivity of metals/alloys in seawater Platinum Gold Graphite Titanium Silver (inert) 316 Stainless Steel Based on Table 17.2, Callister Nickel (passive) 7e . (Source of Table 17.2 is more cathodic M.G. Fontana, Corrosion Copper Engineering , 3rd ed., McGraw- Nickel (active) Hill Book Company, 1986.) Tin Lead 316 Stainless Steel Iron/Steel Aluminum Alloys (active) Cadmium Zinc more anodic Magnesium Chapter 17 -12 FORMS OF CORROSION • Stress corrosion Stress & corrosion • Uniform Attack work together • Erosion-corrosion Oxidation & reduction at crack tips. Break down of passivating occur uniformly over layer by erosion (pipe surface. elbows). • Selective Leaching • Pitting Preferred corrosion of Forms Downward propagation one element/constituent of small pits & holes. of Fig. 17.17, Callister 7e . (e.g., Zn from brass (Cu-Zn)). (Fig. 17.17 from M.G. corrosion Fontana, Corrosion • Intergranular Engineering , 3rd ed., Corrosion along McGraw-Hill Book grain boundaries, • Galvanic Company, 1986.) • Crevice Between two often where special Dissimilar metals are pieces of the same metal. phases exist. physically joined. The Rivet holes g.b. more anodic one prec. corrodes.(see Table 17.2) Zn & Mg attacked Fig. 17.15, Callister 7e . (Fig. 17.15 is zones very anodic. courtesy LaQue Center for Corrosion Technology, Inc.) Fig. 17.18, Callister 7e . Chapter 17 -13 CONTROLLING CORROSION Metal oxide • Self-protecting metals! Metal (e.g., Al, -- Metal ions combine with O stainless steel) to form a thin, adhering oxide layer that slows corrosion. • Reduce T (slows kinetics of oxidation and reduction) • Add inhibitors -- Slow oxidation/reduction reactions by removing reactants (e.g., remove O 2 gas by reacting it w/an inhibitor). -- Slow oxidation reaction by attaching species to the surface (e.g., paint it!). • Cathodic (or sacrificial) protection -- Attach a more anodic material to the one to be protected. e.g., zinc-coated nail e.g., Mg Anode Zn 2+ Adapted from Fig. 17.22(a), Adapted Cu wire from Fig. e- Callister 7e . (Fig. 17.22(a) is zinc zinc from M.G. Fontana, Corrosion 17.23, steel Mg Mg 2+ Callister 2e- 2e- Engineering , 3rd ed., McGraw-Hill pipe anode Book Co., 1986.) 7e . steel Earth Chapter 17 -14 Chapter 17 -15 SUMMARY • Corrosion occurs due to: -- the natural tendency of metals to give up electrons. -- electrons are given up by an oxidation reaction. -- these electrons then used in a reduction reaction. • Metals with a more negative Standard Electrode Potential are more likely to corrode relative to other metals. • The Galvanic Series ranks the reactivity of metals in seawater . • Increasing T speeds up oxidation/reduction reactions . • Corrosion may be controlled by: -- using metals which form -- adding inhibitors a protective oxide layer -- painting -- reducing T -- using cathodic protection. Chapter 17 -16.
Recommended publications
  • GALVANIC/DISSIMILAR METAL CORROSION What It Is and How to Avoid It ASSDA Technical FAQ No 1 1 Edition 2, May 2009

    GALVANIC/DISSIMILAR METAL CORROSION What It Is and How to Avoid It ASSDA Technical FAQ No 1 1 Edition 2, May 2009

    AUSTRALIAN STAINLESS STEEL DEVELOPMENT ASSOCIATION GALVANIC/DISSIMILAR METAL CORROSION What it is and how to avoid it ASSDA Technical FAQ No 1 1 Edition 2, May 2009 Contact between dissimilar metals Metal to metal contact The graph shows that stainless steels have occurs frequently but is often not two ranges of potential. The usual, passive Galvanic corrosion can only occur if the a problem. The aluminium head behaviour is shown by the light hatching. dissimilar metals are in electrical contact. However, if the passive film breaks down, on a cast iron block, the solder on The contact may be direct or by an the stainless steel corrodes and its a copper pipe, galvanising on a external pipe or wire or bolt. If the potential is in the dark bar range. steel purlin and the steel fastener dissimilar metals are insulated from each in an aluminium sheet are common other by suitable plastic strips, washers or As a rule of thumb, if the potential examples. sleeves then galvanic corrosion cannot difference is less than 0.1 volt, then it is occur. Paint is not a reliable electrical unlikely that galvanic corrosion will be significant. WHAT CAUSES GALVANIC insulator especially under bolt heads or CORROSION? nuts or washers or near edges of sheets of If all three conditions are met then metal. The paint is usually damaged on galvanic corrosion is probable and the rate For galvanic or dissimilar or installation or by subsequent movement. of corrosion will be influenced by the electrolytic corrosion to occur, Note that the chromium oxide film layer relative area and the current density three conditions must be met: on the stainless steel is very thin and not delivered by the noble metal.
  • Development of a Low Resistance Low Corrosion Cathode Plate

    Development of a Low Resistance Low Corrosion Cathode Plate

    Development of a low resistance, low corrosion cathode plate for electrowinning and electrorefining Nigel J. Aslin1*1, Christian Pasten2, Addin Pranowo3, Graham J. Heferen4 1. Glencore Technology, Australia ABSTRACT For nearly 40 years Glencore Technology (formerly Mount Isa Mines Copper Refineries) has been the mainstay supplier of permanent cathode plates to the copper industry with its ISA PROCESS and KIDD PROCESS cathode plates. Improvement to the cathode plate design remains a key area for research, and on-going developments by Glencore Technology have led to the commercialisation of a new design. The ISAKIDD cathode plate is universally suited to both electro-refining and electro- winning bringing major cost efficiencies to the operations through improvements in hanger bar strength, corrosion resistance and electrical conductivity. A variation of the this design uses a ‘steer- horn’ shaped hanger bar to lower the resistance path across the cathode plate giving significant tank- house power savings in electrowinning refineries. Technical aspects and results of commercial trials of the ISAKIDD and ‘HP’ cathode plate are discussed in this paper. A novel new contact system which allows shorting frames to be used with Stainless Steel hanger bars will also be tested. Trial results will demonstrate savings in a typical EW tankhouse of up to 720k USD per year in power costs alone, with further savings in maintenance costs and operational efficiencies. *Corresponding author: Glencore Technology, Technical Manager, c/- Copper Refineries Pty Ltd, Hunter St, Stuart, 4811, QLD, Australia. Phone: +61 418887034. Email: [email protected] 1 INTRODUCTION Glencore Technology were the pioneers of Permanent cathode technology for copper and remain committed to continuous improvement and innovation of the technology forty years later.
  • Galvanic Corrosion

    Galvanic Corrosion

    10 GALVANIC CORROSION X. G. ZHANG Teck Metals Ltd., Mississauga, Ontario, Canada A. Introduction graphite, are dispersed in a metal, or on a ship, where the B. Definition various components immersed in water are made of different C. Factors in galvanic corrosion metal alloys. In many cases, galvanic corrosion may result in D. Material factors quick deterioration of the metals but, in other cases, the D1. Effects of coupled materials galvanic corrosion of one metal may result in the corrosion D2. Effect of area protection of an attached metal, which is the basis of cathodic D3. Effect of surface condition protection by sacrificial anodes. E. Environmental factors Galvanic corrosion is an extensively investigated subject, E1. Effects of solution as shown in Table 10.1, and is qualitatively well understood E2. Atmospheric environments but, due to its highly complex nature, it has been difficult to E3. Natural waters deal with in a quantitative way until recently. The widespread F. Polarity reversal use of computers and the development of software have made G. Preventive measures great advances in understanding and predicting galvanic H. Beneficial effects of galvanic corrosion corrosion. I. Fundamental considerations I1. Electrode potential and Kirchhoff’s law I2. Analysis B. DEFINITION I3. Polarization and resistance I4. Potential and current distributions When two dissimilar conducting materials in electrical con- References tact with each other are exposed to an electrolyte, a current, called the galvanic current, flows from one to the other. Galvanic corrosion is that part of the corrosion that occurs at the anodic member of such a couple and is directly related to the galvanic current by Faraday’s law.
  • Galvanic Corrosion Final

    Galvanic Corrosion Final

    GALVANIC CORROSION by Stephen C. Dexter, Professor of Applied Science and Marine Biology, (302) 645-4261 Galvanic corrosion, often misnamed “electrolysis,” is one common form of corrosion in marine environments. It occurs Table 1 when two (or more) dissimilar metals are brought into electri- GALVANIC SERIES cal contact under water. When a galvanic couple forms, one of In Flowing Seawater the metals in the couple becomes the anode and corrodes faster than it would all by itself, while the other becomes the cathode Voltage Range of Alloy and corrodes slower than it would alone. Either (or both) metal Alloy vs. Reference Electrode* in the couple may or may not corrode by itself (themselves) in MagnesiumAnodic or -1.60 to -1.63 seawater. When contact with a dissimilar metal is made, how- Active End ever, the self-corrosion rates will change: corrosion of the Zinc -0.98 to -1.03 anode will accelerate; corrosion of the cathode will decelerate Aluminum Alloys -0.70 to -0.90 or even stop. We can use the seawater Galvanic Series, shown Cadmium -0.70 to -0.76 in Table 1, to predict which metal will become the anode and Cast Irons -0.60 to -0.72 how rapidly it will corrode. Steel -0.60 to -0.70 Aluminum Bronze -0.30 to -0.40 The seawater Galvanic Series is a list of metals and alloys Red Brass, Yellow Brass, ranked in order of their tendency to corrode in marine environ- Naval Brass -0.30 to -0.40 ments. If any two metals from the list are coupled together, the Copper -0.28 to -0.36 one closer to the anodic (or active) end of the series, the Lead-Tin Solder (50/50) -0.26 to -0.35 upper end in this case, will be the anode and thus will corrode Admiralty Brass -0.25 to -0.34 faster, while the one toward the cathodic (or noble) end will Manganese Bronze -0.25 to -0.33 corrode slower.
  • Corrosion Basics

    Corrosion Basics

    CORROSION BASICS (from Swain (1996) and Schultz (1997)) What is corrosion? • Webster’s Dictionary - corrode (v.) To eat away or be eaten away gradually, especially by chemical action. • NACE Corrosion Basics - corrosion may be defined as the deterioration of a material (usually a metal) because of a reaction with the environment. Why do metals corrode? Most metals are found in nature as ores. The manufacturing process of converting these ores into metals involves the input of energy. During the corrosion reaction the energy added in manufacturing is released, and the metal is returned to its oxide state. Metal Ore reduction (add electrons)→ Metal oxidation (strip electrons)→ Corrosion Products In the marine environment, the corrosion process generally takes place in aqueous solutions and is therefore electrochemical in nature. Corrosion consequences Economic - corrosion results in the loss of $8 - $126 billion annually in the U.S. alone. This impact is primarily the result of: 1. Downtime 2. Product Loss 3. Efficiency Loss 4. Contamination 5. Overdesign Safety / Loss of Life Corrosion can lead to catastrophic system failures which endanger human life and health. Examples include a 1967 bridge collapse in West Virginia which killed 46. The collapse was attributed to stress corrosion cracking (SCC). In another example, the fuselage of an airliner in Hawaii ripped open due to the combined action of stress and atmospheric corrosion. Corrosion cell Corrosion occurs due to the formation of electrochemical cells. In order for the corrosion reaction to occur five things are necessary. If any of these factors are eliminated, galvanic corrosion will not occur. THIS IS THE KEY TO CORROSION CONTROL! The necessary factors for corrosion to proceed are: 1.
  • 19. the Galvanic (Electrochemical) Series

    19. the Galvanic (Electrochemical) Series

    19. THE GALVANIC (ELECTROCHEMICAL) SERIES INTRODUCTION All conductive elements (all metals) have different electrical potentials. These electrical potentials put each metal in a hierarchy of activity, with the most active metals at the top of the lists, and the least active at the bottom. This order of electrochemical activity is called the Galvanic Series. A metal higher in the Galvanic Series will corrode preferentially to a metal below it in the Series. The greater the distance apart the metals are in the Galvanic Series, the higher the current that will fl ow between them if they are connected in the presence of an electrolyte (a conducting solution; usually water containing dissolved salts). Some metals like aluminium and zinc develop tough oxide fi lms. These fi lms give them exceptionally good corrosion resistance, although they are among the most active metals. The position of zinc on the Galvanic Series, above most other metals, means that it will corrode preferentially if it contacts any of these metals and moisture is present. This characteristic of zinc is an important part of its exceptional performance in protecting steel from corrosion. Many steel products are galvanized using continuous galvanizing processes. These semi-fabricated steel items (columns, beams, angles etc.) are subject to further processes like slitting, cutting, drilling, punching and welding. This leaves the steel uncoated on cut edges and other areas damaged by processing. The galvanic protection provided by the adjacent zinc coating provides these steel products with their anti-corrosion performance, otherwise rapid corrosion would occur on these exposed areas. A counter example occurs with chrome-plated steel.
  • Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM

    Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM

    metals Article Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM Armen Kvryan, Kari Livingston, Corey M. Efaw, Kyle Knori, Brian J. Jaques, Paul H. Davis, Darryl P. Butt and Michael F. Hurley * Department of Materials Science and Engineering, College of Engineering, Boise State University, Boise, ID 83725-2090, USA; [email protected] (A.K.); [email protected] (K.L.); [email protected] (C.M.E.); [email protected] (K.K.); [email protected] (B.J.J.); [email protected] (P.H.D.); [email protected] (D.P.B.) * Correspondence: [email protected]; Tel.: +1-208-426-4075 Academic Editors: Vineet V. Joshi and Alan Meier Received: 3 February 2016; Accepted: 6 April 2016; Published: 19 April 2016 Abstract: The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy (SKPFM) was used to map the Volta potential differences. Co-localization of SKPFM with Energy Dispersive Spectroscopy (EDS) measurements enabled spatially resolved correlation of potential differences with composition and subsequent galvanic corrosion behavior. Following exposure to the aggressive solution, corrosion damage morphology was characterized to determine the mode of attack and likely initiation areas. When exposed to 0.6 M NaCl, corrosion occurred at the braze-316L interface preceded by preferential dissolution of the Cu-rich phase within the braze alloy. Braze corrosion was driven by galvanic couples between the braze alloys and stainless steel as well as between different phases within the braze microstructure.
  • Galvanic Corrosion Prevention Guide for Water Cooling Systems

    Galvanic Corrosion Prevention Guide for Water Cooling Systems

    WATER COOLED DEVICES Galvanic Corrosion Prevention Guide for Water Cooling Systems November 2017 | White Paper Water Created by Cooled Helen E. Kane, Advanced Energy Industries, Inc. Devices Abstract Table of Contents This report details best practices for reducing the risk of galvanic corrosion in water cooling system designs. Galvanic Summary and Background 2 corrosion will manifest if the following conditions exist: Research Findings 2 Best Practices Recommendations 5 1 Electrically dissimilar metals in contact (or both in References 7 contact with the same water) 2 Electrolyte present (could be as simple as condensation) Time is another critical factor. The mean time to failure can be short or long, depending on the combination of conditions 1 and 2. This report provides the galvanic series for general metals and compatibility. In addition, it lists preventative measures to avoid issues in open loop cooling water systems. 2 GALVANIC CORROSION PREVENTION GUIDE FOR WATER COOLING SYSTEMS Summary and Background This report details best practices for reducing the risk of galvanic corrosion in mechani- cal and electro-mechanical cooling system designs. Galvanic corrosion, sometimes called bimetallic or dissimilar metal corrosion, is when one metal in a system experiences corrosion due to an electro-chemical reaction with a different metal and an electrolyte in the same system. Galvanic corrosion has been experienced in designs with dissimilar metals used in Advanced Energy products that use water cooling. Because conditions that promote gal- vanic reactions can exist inside Advanced Energy units due to the environment and running conditions, some simple best practices will help reduce the risk of galvanic corrosion failure.
  • Corrosion of Base Metals in Contact To� Index the Susceptibility of Different Base Metals to Corrosion While in the Potential for Corrosion Is Very High

    Corrosion of Base Metals in Contact To Index the Susceptibility of Different Base Metals to Corrosion While in the Potential for Corrosion Is Very High

    4300 Catalog General Technical Return Corrosion of Base Metals in Contact To Index The susceptibility of different base metals to corrosion while in the potential for corrosion is very high. Aluminum, being more contact, depends upon the difference between the contact po- anodic metal, will corrode in this combination. tentials, or the electromotive voltages of the metals involved. The greater the potential difference is, the greater is the tendency for As a general guideline, if the metals are half the length of the corrosion. The metal with the higher potential forms the anode chart or more apart, the combination should be avoided. Also, and is corroded. In other words, the larger the separation distance it is not a good idea to combine an anodic metal part with thin in the electromotive chart between the two metals in contact, cross section, such as thin wall tubing, with a cathodic or less the higher the contact potential and chances for corrosion. For anodic metal part of a heavy cross section, such as a fitting. example, zinc and aluminum are very short distance apart in the Example: A thin wall brass tube with steel fitting is a better, chart; therefore potential for corrosion when these two metals are although not ideal, combination than a thin wall steel tube with in contact is very low. On the other hand, aluminum and passiv- brass fitting. ated 316 stainless steel are far apart; hence, when in contact, Electromotive or Galvanic Series for Metals + Anodic Magnesium (least noble) Magnesium alloys corroded Zinc (Parker steel fittings
  • UNITED STATES DEPARTMENT of AGRICULTURE Rural Electrification Administration BULLETIN 1751F-670

    UNITED STATES DEPARTMENT of AGRICULTURE Rural Electrification Administration BULLETIN 1751F-670

    UNITED STATES DEPARTMENT OF AGRICULTURE Rural Electrification Administration BULLETIN 1751F-670 SUBJECT: Outside Plant Corrosion Considerations TO: All Telephone Borrowers REA Telephone Staff EFFECTIVE DATE: Date of Approval EXPIRATION DATE: Seven years from effective date OFFICE OF PRIMARY INTEREST: Outside Plant Branch, Telecommunications Standards Division PREVIOUS INSTRUCTIONS: This bulletin replaces REA Telecommunications Engineering & Construction Manual (TE&CM) 670, Corrosion Considerations in Telecommunications in Outside Plant, Issue 2, dated January 1982. FILING INSTRUCTIONS: Discard REA Telecommunications Engineering & Construction Manual (TE&CM) 670, Corrosion Considerations in Telecommunications in Outside Plant, Issue 2, dated January 1982, and replace it with this bulletin. File with 7 CFR 1751 and on REANET. PURPOSE: This bulletin provides REA borrowers, consulting engineers, contractors and other interested parties with information concerning the various aspects of corrosion which should be considered in the preparation of a system design. Blaine D. Stockton, Jr. 09/02/93 ______________________________ __________________________ Administrator Date Bulletin 1751F-670 Page 2 TABLE OF CONTENTS 1. General . 6 2. Corrosion Theory . 6 3. Types of Corrosion . 8 4. Corrosion Behavior of Metals Used in Outside Plant Construction . 15 5. Corrosion Prevention Measures . 19 6. Environmental Conditions Affecting the Selection of Cable or Wire Shields . 23 7. Soil Measurements . 27 TABLES & FIGURES Table 1 Galvanic Series of Metals in Sea Water . 10 Table 2 Soil Corrosivity Versus Resistivity . 27 Table 3 Typical Soil Resistivity Values . 28 Figure 1 Example of Galvanic Corrosion . 30 Figure 2 Example of Concentration Cell Corrosion . 31 Figure 3 Example of Stray Current Corrosion . 32 Figure 4 Anchor Rod Corrosion - Galvanic Couple . 33 Figure 5 Anchor Rod Corrosion - Differential Aeration Cell 34 Figure 6 Coordinated Stray Current Protection .
  • WJE Primer: Galvanic Corrosion

    WJE Primer: Galvanic Corrosion

    PRIMER BY ELISE M. LOVE, P.E. Wiss, Janney, Elstner Associates, Inc. Galvanic Corrosion At the detail design stage, careful consideration must be given to the compatibility of building materials or systems used in structural and architectural applications. One potential consequence of incompatibility (termed ‘galvanic action’). The more ‘active’ A phenomenon known is accelerated corrosion of metals, which can metal will support the oxidation reaction and occur if dissimilar metals are combined in corrode (becoming the anode, where metal as galvanic corrosion certain environments. This is galvanic will be consumed), while the more ‘noble’ occurs when dissimilar corrosion. Evaluations of compatibility are metal will support the reduction reaction metals, subjected to increasing in importance, as the array of (becoming the cathode, where metal will not potential building materials is ever-expanding. be consumed). the same environment, Fortunately, durability issues related to comprised of a conducting galvanic corrosion can be minimized or The Galvanic Series prevented with proper design. solution, are in direct Compatibility of different metals can be electrical contact. assessed, relative to the potential for galvanic Galvanic Corrosion Defined corrosion, with the use of charts depicting In general, corrosion in metals is an the galvanic (or electromotive force) series in electrochemcial reaction with the different environments. The galvanic series surrounding environment consisting of two indicates which dissimilar metal will tend to partial reactions: an oxidation reaction and corrode (anode) and which dissimilar metal a reduction reaction. When different metals, will tend to support the reduction reaction or metal alloys, are placed in a corrosive (cathode), when the requirements for galvanic environment, each metal develops a potential corrosion are met.
  • Modeling Galvanic Corrosion in Cadmium and Zinc-Nickel Plating Systems Using Mixed Potential Theory

    Modeling Galvanic Corrosion in Cadmium and Zinc-Nickel Plating Systems Using Mixed Potential Theory

    Engineering, Test & Technology Boeing Research & Technology Chemical Technology Modeling Galvanic Corrosion in Cadmium and Zinc-Nickel Plating Systems using Mixed Potential Theory Kristen S. Williams, Joel Thompson, and Peter Kole Boeing Research & Technology Presented at ASETSDefense Workshop 2018 Presented at 2018 NACE CORROSION Conference and Expo Denver, CO, August 21-23, 2018 Research in Progress (RIP) Symposium: Modeling & Simulation Paper #C2018-12037 EAR99 – No License Required Phoenix, AZ, April 15-19, 2018 Outline ▪ Introduction ▪ Galvanic Corrosion in Aircraft – A Combinatorial Challenge! ▪ Problem Statement ▪ Technical Approach & Modeling Methods ▪ Case Study: Zn-Ni Electroplating ▪ Motivation for Research ▪ Model Assumptions ▪ Results ▪ Predicted Galvanic Corrosion Rates of Electroplated Steel ▪ Steel Coupled to Plating: Cd and Zn-Ni ▪ Atmospheric Corrosion Test Results ▪ Conclusions ▪ Future Work / Needs ▪ Acknowledgments ASETSDefense Workshop, August 21-23, 2018 EAR99 – No License Required Paper #C2018-12037 | 2 Introduction Galvanic Corrosion Risks in Aircraft Example: Identifying material contacts for a single surface (Section 44 passenger floor) Blue surfaces: all surfaces of differing material contacting the surface of interest in any way Green splines: can be any (0D, 1D, 2D, 3D) kind of spline; each one represents a material contact (here, 45 contacts for a single surface) Red surface: ‘SECTION_44-- passenger_floor’ (surface of interest) Note: Aircraft model is notional and does not correspond to a ASETSDefense Workshop, August 21-23, 2018 formal engineering drawing. EAR99 – No License Required Paper #C2018-12037 | 3 Galvanic Corrosion Risk – Greater than the sum of the parts Example: Notional geometric model of commercial aircraft. Random assignment of materials. 1. Read in aircraft geometry 3076 parts 2. Assign materials to geometry 3.