THE ENGINEERS CI/SfB & ARCHITECTS' Yu1 GUIDE: HOT DIP GALVANIZING Galvanizers Association provides RIBA CPD assessed material: Literature The Engineers & Architects' Guide: Hot Dip Galvanizing The Engineers & Architects' Guide to Nuts and Bolts Seminar "Corrosion protection of steel by Hot Dip Galvanizing" For further information contact Nicky Smith on 0121 355 8838 or email [email protected] Front Cover: Bellmouth Passage Footbridge, Techniker & Patel Taylor, Peter Cook / View THE ENGINEERS & ARCHITECTS' GUIDE: HOT DIP GALVANIZING Galvanizers Association would like to know what you think of our services and the information we provide. Please use the response sheet on page 51 for your comments on the Guide or for any further information and advice that you may require. If you prefer, an online comment form is available at www.hdg.org.uk/feedback THE ENGINEERS & ARCHITECTS' GUIDE HOT DIP GALVANIZING INTRODUCTION STEEL IS A STRONG, VERSATILE AND INEXPENSIVE Hot dip galvanizing has many benefits Our technical team is on hand to give an MATERIAL WITH USES IN MANY DIFFERENT as a method of corrosion protection. immediate answer to all your queries about Importantly, it will: galvanizing. GA also monitors regulations, INDUSTRIES. IT HAS, HOWEVER, ONE MAJOR takes a leading role in standards development DISADVANTAGE: IT IS PRONE TO CORROSION, s¬PROVIDE¬STEEL¬WITH¬A¬COATING¬WHICH and oversees research projects to support EVEN IN INTERIOR ENVIRONMENTS CORROSION has a long, predictable and and develop the industry. PREVENTION IS THEREFORE ESSENTIAL IF STEEL maintenance free life. GA can also visit your company to give a STRUCTURES ARE TO BE ECONOMICAL. s¬BE¬HIGHLY¬COMPETITIVE¬ON¬A¬FIRST¬ presentation which is approved by RIBA for cost basis Continuing Professional Development (CPD). TODAY, INCREASED AWARENESS OF THE LONG-TERM GA publishes a wide range of technical SAVINGS POSSIBLE FROM REDUCED MAINTENANCE s¬BE¬THE¬MOST¬ECONOMIC¬WAY¬ literature, surveys the market and its to protect steel over long periods trends and improves communications COSTS HAVE HIGHLIGHTED THE NEED FOR DURABLE about galvanizing. PROTECTIVE SYSTEMS FOR STEEL. THIS GUIDE s¬BE¬A¬SUSTAINABLE¬SOLUTION HAS BEEN PRODUCED TO ASSIST DESIGNERS, SPECIFIERS, FABRICATORS AND USERS OF This Guide is published by Galvanizers Association, which represents the hot dip STEELWORK TO DEVELOP THE MOST EFFECTIVE, galvanizing industry of the UK and Ireland. PRACTICAL AND ECONOMIC SOLUTIONS. It contains the essential information needed by architects, consulting engineers and others in selecting a corrosion protection system. The Guide details the protection given by hot dip galvanizing, where and how to use it and how to specify it. There is also information on the process itself and the economic advantages of galvanizing. Galvanizers Association (GA) has provided authoritative information and advice on hot dip galvanizing to users and potential users since it was first established in 1949. E&A INTRODUCTION 04 THE ENGINEERS & ARCHITECTS' GUIDE HOT DIP GALVANIZING CONTENT SUBJECT CONTENT PAGE _ _ _ ONE - Galvanizing and the environment - Zinc - natural & essential for health 06 GALVANIZING & SUSTAINABLE - Recycling & the environment CONSTRUCTION - GalvAction 21 - taking the galvanizing industry forward TWO - Preparation - The coating, Coating thickness 10 AN INTRODUCTION TO - The galvanizing process - Post-treatments for galvanizing, HOT DIP GALVANIZING Size of articles THREE - Cohesion - Toughness 14 PHYSICAL PERFORMANCE FOUR - Atmospheric corrosion resistance - Performance in other environments 16 CORROSION PERFORMANCE - The Zinc Millennium Map FIVE - Barrier protection - Protection by sacrificial action 22 HOW GALVANIZING PROTECTS STEEL SIX - Economics - Lifetime costs 24 COSTS AND ECONOMICS - Initial cost SEVEN - Standards - Lead times 28 SPECIFYING HOT DIP GALVANIZING - Fasteners - Appearance EIGHT - Filling, venting and drainage - Strength 30 DESIGNING ARTICLES - Base metal and combinations - Welding FOR GALVANIZING - Size and shape - Labelling and marking - Fasteners - Masking, - Overlapping surfaces - Connections - Castings - Handling of articles - Moveable parts, - Surface contamination - Distortion NINE - Quality assurance - Coating finish 40 QUALITY AND INSPECTION - Coating weight or thickness - Renovating damaged coatings measurement TEN - Hot dip galvanized threaded fasteners - Rust prevention at welds 44 JOINING GALVANIZED STEEL - Welding galvanized steel ELEVEN - Preparation of galvanized steel - Guidelines for painting and 46 PAINTING AND POWDER COATING powder coating OF GALVANIZED STEEL TWELVE - British Standards - Swedish Standards 48 RELEVANT STANDARDS - ASTM Standards - ISO Standards - DIN Standards - Australian Standards THIRTEEN - Advisory services 50 ADVISORY SERVICES 05 THE ENGINEERS & ARCHITECTS' GUIDE HOT DIP GALVANIZING SECTION ONE GALVANIZING AND SUSTAINABLE CONSTRUCTION SECTION ONE _ TITLE GALVANIZING AND SUSTAINABLE CONSTRUCTION _ FUTURE TECHNOLOGIES WILL BE LOW ENERGY LOW WASTE. GALVANIZING IS A RECYCLABLE SOLUTION THAT REDUCES THE ENERGY DEMAND OF STRUCTURES. The pressures on global industry to accept environmental responsibility GALVANIZING AND In the galvanizing process, iron or steel for its actions is wholly justified, given society’s quest for sustainability. THE ENVIRONMENT articles are dipped into a bath containing _ molten zinc just above its melting point. The philosophy of sustainability is quite simple and is concerned with Any zinc that does not form a coating on the ensuring a better quality of life for everyone - now and, importantly, Galvanizing, the coating of iron or steel metal remains in the bath for further re-use. for generations to come. The concept is common sense based on with zinc, is probably the most Galvanizing residues are recovered and zinc substantial criteria and principles. It sets out to meet four objectives: environmentally friendly process available recycled for further use. to prevent corrosion. It is estimated that s¬3OCIAL¬PROGRESS ¬WHICH¬RECOGNISES¬THE¬NEEDS¬OF¬EVERYONE corrosion costs around 4% of GDP in As well as zinc recovered from these the USA. Effective corrosion protection residues, recycled zinc from other sources, s¬-AINTENANCE¬OF¬HIGH¬AND¬STABLE¬LEVELS¬OF¬ECONOMIC¬GROWTH¬ is a vital means of reducing the energy such as zinc scrap, is often used in and employment demands of buildings and structures. galvanizing. Galvanized steel can be recycled easily with other steel scrap in the steel s¬%FFICIENT¬PROTECTION¬OF¬THE¬ENVIRONMENT Every 90 seconds, across the world, one production process. tonne of steel turns to rust; of every two s¬0RUDENT¬USE¬OF¬NATURAL¬RESOURCES tonnes of steel made, one is to replace rust. Improvements in gas burner technology have also greatly improved energy efficiency in In respect of efficient protection of the environment and prudent use Use of hot dip galvanizing to prevent rust heating the galvanizing bath. Exhaust heat is of natural resources, the hot dip galvanizing process stands up to means that for every one tonne of steel not wasted and is used to heat pre-treatment scrutiny and can be considered as a major contributor towards protected we conserve enough energy to chemicals or dry work prior to immersion. sustainable construction. satisfy an average family’s energy needs for several weeks. The galvanizing industry is committed to understanding and improving the life-cycle Galvanizing is efficient in its use of zinc to environmental performance of its process protect steel for very extensive periods - and products. Galvanizers Association has saving energy and resources with minimal recently helped establish a Pan-European impact on the environment. Galvanizing Life Cycle Inventory database for general will protect steel structures for decades galvanizing. This LCI data will allow and minimises maintenance. Environmental Product Declarations and other life cycle assessments to be made Zinc, the natural element responsible for this on structures involving galvanized steel. corrosion resistance, is indispensable for humans, animals and plants. 06 THE ENGINEERS & ARCHITECTS' GUIDE HOT DIP GALVANIZING SECTION ONE GALVANIZING AND SUSTAINABLE CONSTRUCTION Process emissions Process emissions from the galvanizing process are very low. Aqueous discharge - all waste liquids - which consist mainly of spent acids used to prepare the steel, are removed by licensed waste management companies in accordance with mandatory procedures, thus protecting surface and ground water. Spent acid is also increasingly used to neutralise other wastes and in the manufacture of water treatment chemicals. The industry has greatly improved its utilisation of process chemicals in recent years - reducing the volumes of acid used per tonne of steel processed. Emissions to the atmosphere are inherently very low and are strictly governed by the Environmental Protection Act. Galvanizing baths must capture their particulate emissions to air. This is successfully accomplished by the use of bath enclosures together with filters. A survey by the Environment Technology Best Practice Programme concluded that “Galvanizers use less than 25 litres of water per tonne of product, compared with 2000 litres in the general metal finishing industry”. 07 THE ENGINEERS & ARCHITECTS' GUIDE HOT DIP GALVANIZING SECTION ONE GALVANIZING AND SUSTAINABLE CONSTRUCTION Total Scrap Old Scap automobiles, appliances, die-cast parts, galzanized steel Secondary Zinc Process Scap offcuts, Zinc Ore from production trimmings, galvanizing mine