16.3 Laboratory testing of paint films 16.3.1 Determination of drying time 16.3.2 Gloss 6.3.3 Hiding power 6.3.4 Adhesion tests 16.3.5 Abrasion 16.3.6 Physical state of the film 16.3. 7 Film thickness 6.4 Testing of paints 6.5 Laboratory performance tests 16.5.1 Artificial weathering 16.5.2 Salt-spray tests 16.5.3 Humidity and condensation tests 16.5. 4 Other laboratory tests 16.6 Instruments for specialised analysis 16.7 Field tests 16. 7.1 Type of specimen to be used for the tests 16.7.2 The coating 6.7.3 Exposure of specimens 6.7.4 Test sites 16.7.5 Monitoring of test sites 16.7.6 Methods of measuring atmospheric pollution 16.7.7 Conduct of field tests 16.8 Service trials 6.9 Tests in water and soil 6.10 Formulating the test programme 16.11 Reporting the results of tests References C D.A. Bavliss and D. H. Deacon
16.3 Laboratory testing of paint films 16.3.1 Determination of drying time 16.3.2 Gloss 16.3.3 Hiding power 16.3.4 Adhesion tests 16.3.5 Abrasion resistance 16.3.6 Physical state of the film 16.3.7 Film thickness 16.4 Testing of paints 16.5 Laboratory performance tests 16.5.1 Artificial weathering 16.5.2 Salt-spray tests 16.5.3 Humidity and condensation tests 16.5.4 Other laboratory tests 16.6 Instruments for specialised analysis 16.7 Field tests 16.7.1 Type of specimen to be used for the tests 16.7.2 The coating 16.7.3 Exposure of specimens 16.7.4 Test sites 16.7.5 Monitoring of test sites 16.7.6 Methods of measuring atmospheric pollution 16.7.7 Conduct of field tests 16.8 Service trials 16.9 Tests in water and soil 16.10 Formulating the test programme 16.11 Reporting the results of tests References Contents xiii © 2002 D. A. Bayliss and D. H. Deacon
Acknowledgements The original version and first edition of this book, published in 1985 and 1991 respectively, were largely the inspiration and work of the late Ken Chandler. Ken,s objective was never to provide a comprehensive text book on coating technology but, instead, an easy to read reference for engineers, architects and others, for whom the protection of steelwork is an important, although often a comparatively minor, part of their total professional activities. Nowadays, not only are new materials and methods being developed onstantly but the increased emphasis and legislation on health, safety and environmental issues have made even more radical changes necessary in paint materials, surface preparation and paint application. It has become even more difficult for the non-specialist to keep abreast of the situation The sudden death of Ken Chandler in 1995 was not only a personal loss of a friend and colleague, but deprived the Industry of somebody of great integrity and very long and valuable experience. When requested to produce this new edition I was able to persuade David Deacon, somebody with similar long experience, to become co-author, this despite the many other calls on his time. Fortunately we were both able to gain the services of yet another colleague, namely Garth Cox, whose experience as a senior paint chemist for both major paint manufacturers and raw material suppli ers, has been of invaluable help. I also take this opportunity to acknowledge the work of colleagues in his field. They are too numerous to mention, but many of the views expressed in this book have arisen from discussions with them and the study of their contributions to journals and conferences over many years Derek Bayliss Woodbridge, Suffolk October 2001 C D.A. Bavliss and D. H. Deacon
Acknowledgements The original version and first edition of this book, published in 1985 and 1991 respectively, were largely the inspiration and work of the late Ken Chandler. Ken’s objective was never to provide a comprehensive text book on coating technology but, instead, an easy to read reference for engineers, architects and others, for whom the protection of steelwork is an important, although often a comparatively minor, part of their total professional activities. Nowadays, not only are new materials and methods being developed constantly but the increased emphasis and legislation on health, safety and environmental issues have made even more radical changes necessary in paint materials, surface preparation and paint application. It has become even more difficult for the non-specialist to keep abreast of the situation. The sudden death of Ken Chandler in 1995 was not only a personal loss of a friend and colleague, but deprived the Industry of somebody of great integrity and very long and valuable experience. When requested to produce this new edition I was able to persuade David Deacon, somebody with similar long experience, to become co-author, this despite the many other calls on his time. Fortunately we were both able to gain the services of yet another colleague, namely Garth Cox, whose experience as a senior paint chemist for both major paint manufacturers and raw material suppliers, has been of invaluable help. I also take this opportunity to acknowledge the work of colleagues in this field. They are too numerous to mention, but many of the views expressed in this book have arisen from discussions with them and the study of their contributions to journals and conferences over many years. Derek Bayliss Woodbridge, Suffolk October 2001 © 2002 D. A. Bayliss and D. H. Deacon
Introduction Many Resident Engineers for major building projects nowadays echo the sentiment that 'Painting amounts to 10% of the job but provides 90% of the problems. Yet at the same time there are, unquestionably, large areas of coated steelwork withstanding the most adverse conditions for surpris- ingly long periods. A typical example is the coating of offshore platforms in the North Sea. Even in less exotic circumstances, for example bridge structures inland, engineers have successfully extended repainting cycles by as much as three times compared with practices of only thirty years age The majority of coatings used nowadays have considerably improved properties over the materials used then. However, this is not the sole reason for the success. The following factors have become even more important than previously (i)Coating specifications should say what they mean and mean what they say. See Chapter 8 (ii) Coating manufacturers' recommendations regarding application and suitability of their products for the relevant conditions should be followed as closely as possible. See Chapter 1 (iii) Materials supplied should be of a consistent standard of quality. See Chapter 16 (iv) Surface preparation should be no more or no less than is required to achieve the specified durability. See Chapter 3. (v) Because of the variable performance that can be obtained owing to sometimes even minor differences in the preparation and applica- tion process, the whole operation, ideally, should be monitored by a competent and qualified coating inspector. See Chapter 9 It can be shown. even to the satisfaction of the accountants that in the majority of cases there are substantial economic benefits to be gained in the long term by adopting sound coating practice. In the short term owever, the costs are likely to be higher and this must be appreciated by all concerned(see Section 14.5.2) C D.A. Bavliss and D. H. Deacon
Chapter 1 Introduction Many Resident Engineers for major building projects nowadays echo the sentiment that ‘Painting amounts to 10% of the job but provides 90% of the problems.’ Yet at the same time there are, unquestionably, large areas of coated steelwork withstanding the most adverse conditions for surprisingly long periods. A typical example is the coating of offshore platforms in the North Sea. Even in less exotic circumstances, for example bridge structures inland, engineers have successfully extended repainting cycles by as much as three times compared with practices of only thirty years ago. The majority of coatings used nowadays have considerably improved properties over the materials used then. However, this is not the sole reason for the success. The following factors have become even more important than previously: (i) Coating specifications should say what they mean and mean what they say. See Chapter 8. (ii) Coating manufacturers’ recommendations regarding application and suitability of their products for the relevant conditions should be followed as closely as possible. See Chapter 14. (iii) Materials supplied should be of a consistent standard of quality. See Chapter 16. (iv) Surface preparation should be no more or no less than is required to achieve the specified durability. See Chapter 3. (v) Because of the variable performance that can be obtained owing to sometimes even minor differences in the preparation and application process, the whole operation, ideally, should be monitored by a competent and qualified coating inspector. See Chapter 9. It can be shown, even to the satisfaction of the accountants, that in the majority of cases there are substantial economic benefits to be gained in the long term by adopting sound coating practice. In the short term, however, the costs are likely to be higher and this must be appreciated by all concerned (see Section 14.5.2). © 2002 D. A. Bayliss and D. H. Deacon
As things stand today, there is little wonder that even relatively young engineers seem to yearn for the days when painting steel structures meant little more than a perfunctory wire brushing followed by red lead in oil primer, followed by two coats of gloss paint. Indeed, only about thirty years ago this was the standard paint system for many major structures, such as the structural steelwork of new power stations in the UK. The advantages of such a system were cheapness and foolproofness. Durability was generally only about 4 years for exterior exposure but the process could be repeated without much expense or trouble. However, there is little question that in modern times the slow drying, toxicity(see Chapter 4)and repeated cost of maintenance(see Section 14.5) would be unaccept able. In contrast, today there are several office buildings in London where the exposed steelwork has been painted with a zinc silicate primer and two-pack urethane top-coats. That is a coating system with probably the greatest durability and least tolerance during application(see Chapter 4) Also there are structures with very limited and expensive access that are being painted with three coats of moisture-cured urethane during the course of one day, even under damp and other adverse conditions(see Section 4.9.3.5) In fact, this revolution in the paint industry could really be said to have started back in 1938. Dr Pierre Castan of Switzerland, a chemist working for a firm making dentures, invented epoxy resins. A Swiss patent for the invention was filed in 1940 and for a curing agent in 1943. However, the firm was unable to exploit the discovery sufficiently in the dental field and sold the rights to what is now CIBA-Geigy. They started to market epoxy resins, under the tradename Araldite, in 1946. Subsequently Shell (USA) also purchased the patent and marketed under the tradenames Epon and Epikote. However, it was at least a decade later that such materials began to be accepted for such specialist operations as tank lining Other synthetic resins also became available, including chlorinated rubbers and vinyls, etc, but it was urethanes and epoxies in their infinite variety that led to many complications. Then, in the 1990s, it was the impact of environmental legislation and health and safety controls with the requirement for low vOc-compliant coatings (see Chapter 4)which resulted in major changes in coating technology. Many favourite coating such as chlorinated rubber and coal tar epoxy, with a proven history of long-term durability for wet or immersed surfaces, had to be phased out because of high solvent content and toxicity problems. The result has been substitution with newer, less familiar materials or methods of application. It is no wonder that engineers and others often find the subject confusing The development of quick-drying, high-build coatings has also brought another complication, namely the need for high standards of surface preparation. Even for the old-established oleo-resinous systems, it has been known for many years that application on to cleaned surfaces, such C D.A. Bavliss and D. H. Deacon
As things stand today, there is little wonder that even relatively young engineers seem to yearn for the days when painting steel structures meant little more than a perfunctory wire brushing followed by red lead in oil primer, followed by two coats of gloss paint. Indeed, only about thirty years ago this was the standard paint system for many major structures, such as the structural steelwork of new power stations in the UK. The advantages of such a system were cheapness and foolproofness. Durability was generally only about 4 years for exterior exposure but the process could be repeated without much expense or trouble. However, there is little question that in modern times the slow drying, toxicity (see Chapter 4) and repeated cost of maintenance (see Section 14.5) would be unacceptable. In contrast, today there are several office buildings in London where the exposed steelwork has been painted with a zinc silicate primer and two-pack urethane top-coats. That is a coating system with probably the greatest durability and least tolerance during application (see Chapter 4). Also there are structures with very limited and expensive access that are being painted with three coats of moisture-cured urethane during the course of one day, even under damp and other adverse conditions (see Section 4.9.3.5). In fact, this revolution in the paint industry could really be said to have started back in 1938. Dr Pierre Castan of Switzerland, a chemist working for a firm making dentures, invented epoxy resins. A Swiss patent for the invention was filed in 1940 and for a curing agent in 1943. However, the firm was unable to exploit the discovery sufficiently in the dental field and sold the rights to what is now CIBA-Geigy. They started to market epoxy resins, under the tradename Araldite, in 1946. Subsequently Shell (USA) also purchased the patent and marketed under the tradenames Epon and Epikote. However, it was at least a decade later that such materials began to be accepted for such specialist operations as tank lining. Other synthetic resins also became available, including chlorinated rubbers and vinyls, etc., but it was urethanes and epoxies in their infinite variety that led to many complications. Then, in the 1990s, it was the impact of environmental legislation and health and safety controls with the requirement for low VOC-compliant coatings (see Chapter 4) which resulted in major changes in coating technology. Many favourite coatings such as chlorinated rubber and coal tar epoxy, with a proven history of long-term durability for wet or immersed surfaces, had to be phased out because of high solvent content and toxicity problems. The result has been substitution with newer, less familiar materials or methods of application. It is no wonder that engineers and others often find the subject confusing. The development of quick-drying, high-build coatings has also brought another complication, namely the need for high standards of surface preparation. Even for the old-established oleo-resinous systems, it has been known for many years that application on to cleaned surfaces, such 2 Steelwork corrosion control © 2002 D. A. Bayliss and D. H. Deacon
as blast-cleaned(see Section 3. 2.3)or pickled(see Section 3. 2.6)gives consistently greater durability than with hand cleaning The production of the first edition of the Swedish Standard photographs of rust and preparation grades in 1946 was a far-sighted work of excep- tional quality for its day. This standard was soon used, or at least paid lip service, by most of the industrial nations In 1978 there was the first meeting of the International Standards Organisation, Sub-committee ISO/TC 35/SC12. The objective of this com- mittee was to produce standards for the preparation of steel substrates before the application of paints and related products. At that date the very few Surface Preparation Standards that existed dealt solely with the visual cleanliness of the surface after cleaning and in particular the absence of millscale. For example, no regard was paid to invisible contaminants such as soluble iron corrosion products hidden at the bottom of corrosion pits n rusted steel, particularly under maintenance conditions. Also the Standards for abrasives specified only their size requirements At the 17th meeting of the International Standards Committee(ISO)TC 36/SC12 ISO committee, held in Sydney, Australia in March 2000, forty- four Standards on'Preparation of steel substrates before application of paints and related products', covering visual cleanliness, tests for surface cleanliness, measurement of surface profile, surface preparation methods nd specifications for metallic and non-metallic abrasives, had been pub- lished. All but one(a Japanese apparatus for measuring chloride by ion detection tube) had become identical British Standards and it was antici- pated that all would become CEn Standards. Other important Standards then still in draft form included: guidance levels of water-soluble contami- nation, preparation grades for welds, cut edges and other steel surface defects, preparation grades after high pressure water jetting and measure- ment of surface profile by replica tape. Unfortunately it takes several years before Committee drafts eventually emerge as published Iso Standards. All this may well make the specifier's task more effective, but certainly ot easier. One suspects that there will be a real danger of demanding the lowest limits of contamination in all circumstances and regardless of the actual requirements. Clearly there is a need for specifiers, who may be practising engineers, architects, designers and others, for whom corrosion control and steelwork protection are a comparatively minor part of their overall, professional responsibility, to understand the implications of coat- ing techi Those fully involved in the field, such as steel fabricators, paint applica- tors, galvanisers and paint manufacturers, have much expertise and advice to offer. full benefit should be taken of such information and background knowledge of the subject will be of considerable assistance. The principles of good corrosion control do not change but the develop ment of new techniques and materials is a continuing process. It is hoped C D.A. Bavliss and D. H. Deacon
as blast-cleaned (see Section 3.2.3) or pickled (see Section 3.2.6) gives consistently greater durability than with hand cleaning. The production of the first edition of the Swedish Standard photographs of rust and preparation grades in 1946 was a far-sighted work of exceptional quality for its day. This standard was soon used, or at least paid lipservice, by most of the industrial nations. In 1978 there was the first meeting of the International Standards Organisation, Sub-committee ISO/TC 35/SC12. The objective of this committee was to produce standards for the preparation of steel substrates before the application of paints and related products. At that date the very few Surface Preparation Standards that existed dealt solely with the visual cleanliness of the surface after cleaning and in particular the absence of millscale. For example, no regard was paid to invisible contaminants such as soluble iron corrosion products hidden at the bottom of corrosion pits on rusted steel, particularly under maintenance conditions. Also the Standards for abrasives specified only their size requirements. At the 17th meeting of the International Standards Committee (ISO) TC 36/SC12 ISO committee, held in Sydney, Australia in March 2000, fortyfour Standards on ‘Preparation of steel substrates before application of paints and related products’, covering visual cleanliness, tests for surface cleanliness, measurement of surface profile, surface preparation methods and specifications for metallic and non-metallic abrasives, had been published. All but one (a Japanese apparatus for measuring chloride by ion detection tube) had become identical British Standards and it was anticipated that all would become CEN Standards. Other important Standards then still in draft form included: guidance levels of water-soluble contamination, preparation grades for welds, cut edges and other steel surface defects, preparation grades after high pressure water jetting and measurement of surface profile by replica tape. Unfortunately it takes several years before Committee drafts eventually emerge as published ISO Standards. All this may well make the specifier’s task more effective, but certainly not easier. One suspects that there will be a real danger of demanding the lowest limits of contamination in all circumstances and regardless of the actual requirements. Clearly there is a need for specifiers, who may be practising engineers, architects, designers and others, for whom corrosion control and steelwork protection are a comparatively minor part of their overall, professional responsibility, to understand the implications of coating technology. Those fully involved in the field, such as steel fabricators, paint applicators, galvanisers and paint manufacturers, have much expertise and advice to offer. Full benefit should be taken of such information and, again, a background knowledge of the subject will be of considerable assistance. The principles of good corrosion control do not change but the development of new techniques and materials is a continuing process. It is hoped Introduction 3 © 2002 D. A. Bayliss and D. H. Deacon