Chapter I Introduction to duplex systems Although belonging to the group of older building and construction materials, steel has remained the most important commodity in to days technology. In comparison with other materials, such as con crete, stone, wood, etc., steel has a number of both technical and economic advantages — i.e., relatively light weight per unit of vol ume of construction, easy repair and addition possibilities, easy formability, wide range of available parts and forms and economical means to assemble parts. Also, from an ecological point of view, steel has attractive characteristics.
Duplex Systems Hot-dip Galvanizing plus Pointing by J.F.H von Eijnsbergen Consultant Coating Technology, The Hague, The Netherlands 1994 ELSEVIER AMSTERDAM — LONDON — NEW YORK — TOKYO ELSEVIER S C I E N C E B.V Sara Burgerhartstraat P.O B o x 1 , 1000 A E Amsterdam, T h e Netherlands Library of Congress Cataloging-in-Publication D a t a Eijnsbergen, J.F.H van Duplex systems: hot-dip galvanizing plus painting / by J.F.H van Eijnsbergen p cm Includes bibliographical references and index ISBN 0-444-81799-9 G a l v a n i z i n g TS660.E36 M e t a l s - P a i n t i n g I T i t l e 1994 672.7'3-dc20 94-5804 CIP ISBN: 444 81799 © 9 , Elsevier S c i e n c e B V All rights reserved N o part o f this p u b l i c a t i o n m a y b e r e p r o d u c e d , s t o r e d in a r e t r i e v a l s y s t e m o r t r a n s m i t t e d in a n y f o r m or b y a n y m e a n s , e l e c t r o n i c , m e c h a n i c a l , p h o t o c o p y i n g , r e c o r d i n g o r o t h e r w i s e , w i t h o u t t h e prior w r i t t e n p e r m i s s i o n o f t h e p u b l i s h e r , E l s e v i e r S c i e n c e B V , C o p y r i g h t & Permissions Department, P.O B o x , 1000 A M A m s t e r d a m , T h e Netherlands S p e c i a l r e g u l a t i o n s for r e a d e r s in t h e U S A : T h i s p u b l i c a t i o n h a s b e e n r e g i s t e r e d w i t h t h e C o p y r i g h t C l e a r a n c e Center Inc ( C C C ) , S a l e m , M a s s a c h u s e t t s Information can b e obtained f r o m t h e C C C a b o u t c o n d i t i o n s u n d e r w h i c h p h o t o c o p i e s o f parts o f t h i s p u b l i c a t i o n m a y b e m a d e in t h e U S A A l l o t h e r c o p y r i g h t q u e s t i o n s , i n c l u d i n g p h o t o c o p y i n g o u t s i d e t h e U S A , s h o u l d b e referred t o t h e P u b l i s h e r N o r e s p o n s i b i l i t y is a s s u m e d b y t h e P u b l i s h e r f o r a n y i n j u r y a n d / o r d a m a g e t o p e r s o n s or property as a matter o f products liability, n e g l i g e n c e or o t h e r w i s e , or f r o m any u s e or operation o f a n y m e t h o d s , p r o d u c t s , i n s t r u c t i o n s o r i d e a s c o n t a i n e d in t h e m a t e r i a l h e r e i n T h e u s e o f p r o d u c t s a n d / o r p r o c e s s e s m e n t i o n e d in t h i s b o o k s h o u l d b e c h e c k e d b y t h e r e a d e r f o r p o s s i b l e p a t e n t s T h e a u t h o r a c c e p t s n o r e s p o n s i b i l i t y for i n e p t u s e o r a n y p a t e n t i n f r i n g e m e n t s T h i s b o o k is p r i n t e d o n a c i d - f r e e p a p e r FOREWORD It gives me great pleasure to write the foreword to this book because it is unique in several respects It is the first comprehensive text ever written on the specialised topic of duplex systems, which is the generic term for painted hot-dip batch-galvanized structural steel Another feature of this book is that both the traditional batch hot-dip galvanizing process and the modern sheet galvanizing processes, such as those used in the automotive and building industries, are covered Furthermore, unlike many other monographs, it offers a combi nation of practical information, which will enable the engineer to select the proper materials in a wide range of different conditions, and scientific background information The practical guidelines given in this book are backed up and supported by an impressive amount of technical and scientific discussions or justifications Even modern surface analysis tools are described and recent applications included The literature is covered until very recently and includes the entire world literature on the subject matter The author of this book has an unsurpassed experience in this field and many of the cited examples of successful (or unsuccessful!) attempts to use duplex systems for corrosion protection of structural steel are drawn from the personal experience that the author has acquired in the past forty years I can, therefore, recommend this book strongly and without reservation to all engineers in the paint, metallurgical or galvanizing industries who come across painted galvanized steels, whether it be for a cursory look at which paint might the trick or for a more in-depth understanding of the mechanism of paint failure in a particu lar environment or application Prof Dr W.J van Ooij Department of Materials Science and Engineering University of Cincinnati Ohio, USA PREFACE "Save the surface and you save all." When I wrote my first book on metal coating in 1939 the above slogan headed the introduction Within the limits of it, this is the basis of the coating industry and its allied branches The enormous costs of corrosion, its prevention, as well as reconditioning corroded surfaces are nowadays well known In industrial countries such costs amount to 3-4 percent of their Gross National Products Duplex systems (galvanizing plus painting) are an important contribution to the corrosion prevention of steel surfaces, which is based on its synergistic effect In this book — the first on this subject in English — I have endeavoured to provide a detailed survey of duplex systems from their beginning in the 1950s to the systems and their applications today The development of modern surface analysis has contributed considerably to an improved knowledge and composition of duplex systems in the 1990s Many international case histories are mentioned in the last chapter A special chapter describes failures in duplex systems, their origins and reconditioning methods I would like to express my gratitude to all who have provided information and/or illustrative material They are, in alphabetical order: AKZO Coatings, Armco Research & Technology, Australian Zinc Development Association, BIEC (European Producers of Gal valume), Cape Galvanising (Pty) Ltd., Centre de Recherches Metal lurgiques (CRM), Clements Corrosiepreventie B.V., Dietsche Holding Co., Duncan Galvanizing Co., Electriciteitsbedrijf ZuidHolland (EZH), European Coil Coaters Association, Galvanizers Association of Australia (GAA), Galvanizers Association of the UK, Geholit + Wiemer GmbH, GemeinschaftsausschuB Verzinken e.V., Hoogovens, International Lead Zinc Research Organisation (ILZRO), MAVOM, National Association of Corrosion Engineers (NACE), Nordisk Forzinkningsforening, K.-A Van Oeterenf, Rembrandtin Lackfabrik, Schaepmans Lakfabrieken/Delta Coatings BV, South African Hot-Dip Galvanizers Association, Stichting Doelmatig Verzinken (SDV), Centre TNO Coatings, VDF Verband der Deutschen Feuerverzinkungsindustrie e.V., Verzinkerij Heerhugowaard BV, Voest Alpine Nederland, Weert Groep BV Very special thanks are due to Prof Dr William van Ooij and Frank C Porter for their valuable suggestions and remarks, to Karla W Nieukerke for her helpful assistance during the writing of this book, Frances Holmes for her meticulous typing of the manuscript, and to Jo and Leon Verstappen for their expert assistance in comput erizing text and illustrations I would also like to express my sincere thanks to the publishers, Elsevier Science, for their valuable cooperation and assistance during the publication of this book Finally, I would like to quote from the 'Immense Journey" by Loren Elseley: " we cannot in one lifetime see all what we would like to see or learn all that we hunger to know " Jan F.H van Eijnsbergen The Hague, The Netherlands 1994 SPONSORS The author and publisher express their gratitude to the following companies and institutions for sponsoring the colour printing in this book - American Galvanizers Association (USA) Asociacion Tecnica Espanola de Galvanizacion (Spain) Associazione Italiana Zincatura (Italy) Bammens Groep BV (The Netherlands) B.E Wedge Holdings Ltd (UK) Billiton Marketing & Trading BV (The Netherlands) B.V Verzinkerij Heerhugowaard (The Netherlands) Cape Galvanising (Pty) Ltd (Republic of South Africa) Galvanizers Association (UK) Galvazinc Association (France) Geholit + Wiemer Lack- und Kunststoff-Chemie GmbH (Germany) Hogeschool Utrecht [HO-U] (The Netherlands) Hoogovens Corporate Research (The Netherlands) Institut fur angewandtes Feuerverzinken GmbH (Germany) International Lead Zinc Research Organization Inc (USA) Nederlands Corrosie Centrum (NCC) (The Netherlands) Nordisk Forzinkningsforening (Sweden) Outokumpu Zinc Oy (Finland) Schaepmans' Lakfabrieken/Delta Coatings BV (The Netherlands) Verband der Deutschen Feuerverzinkungsindustrie e.V (Germany) Vereniging voor Oppervlaktetechnieken van Materialen (VOM) (The Netherlands) Verzinkerij Meerveldhoven BV (The Netherlands) Weert Groep B.V (The Netherlands, Belgium and Germany) Chapter I I n t r o d u c t i o n to d u p l e x s y s t e m s Although belonging to the group of older building and construction materials, steel has remained the most important commodity in to day's technology In comparison with other materials, such as con crete, stone, wood, etc., steel has a number of both technical and economic advantages — i.e., relatively light weight per unit of vol ume of construction, easy repair and addition possibilities, easy formability, wide range of available parts and forms and economical means to assemble parts Also, from an ecological point of view, steel has attractive characteristics The annual world production amounts to approximately 800 million tons This tonnage is divided for 1990 over the following countries or groups thereof [1] Fig 1-1 World European Community (EC-12) Other West-European countries Eastern Europe North America South America Japan Other Asiatic countries Other countries (continents) 138 25 205 100 38 110 75 80 Total approximately Ill About one-third is made from scrap — thus saving considerably on the costs of production, as well as on the costs of raw materials and manufacturing In comparison with a recycling factor of steel of approximately 90, aluminium has 34, glass 45, paper 40 and plastics 10 [2] Also in the sector of corrosion protection, the need for a more sparing use of materials and thus, in connection with their coating systems, a re-assessment of anticorrosive performance versus recyclability will be unavoidable The history, present position and pros pects of zinc recycling are summarized in a recent brochure of the European Zinc Institute [17] Modern duplex systems are already allocations million regions' of steel tons) in 1990 production (in Chapter I fulfilling this combination of characteristics Also, modern research and development in the steel industry has resulted in the use of many special steel types — such as chromium steels, stainless steels, highstrength low-alloy (HSLA) steels and many other alloyed steels which are currently in use for special applications As with all other constructional materials, steel also has unfavour able properties (in this case, just one), namely its surface will rust when exposed to the elements Rust is not a single compound: its composition varies with the type and concentration of atmospheric elements and pollutants, as well as with the degree of humidity and the duration of wetness Rust generally consists of hydrated iron oxides, e.g goethite (α-FeOOH), lepidocrocite (γ-FeOOH), akaganite (β-FeOOH) and/or In sulphur-containing atmospheres, nests of iron magnetite sulphate are present in rust In marine areas, akaganite and salt (NaCl) encrustations are often present in rust [16] See Fig 1-2 The varying types of rust, plus the fact that its volume is roughly twice that of the steel from which it has been formed, are the main technological, economic and ecological reasons for optimally protecting steel surfaces against rust formation and consequential corrosion The corrosion of metal surfaces in general has been published in many handbooks and mono- (Fe3U4) Atmospheric attack Fig 1-2 Composition Sulphate nests: of in rust industrial atmospheres; φ-FeOOH): mainly near/on beaches; (y-FeOOH)+ moist (Fe ) (y-FeOOH) H0 -> (a-FeOOH) in Ψ \7 \/ \7 77 \7 77 Ψ atmospheres; + H0 + in moist Cl~-> beach areas Steel γ-FeOOH Lepidocrocite α-FeOOH Goethite Fe Magnetite β-FeOOH Akaganite Fe-Sulphates ferro,ferri, hydro C Ρ ZnO Ζη~ C oxygen electrode — φ Ό OH' Zn~ ο φ φ Β ^ ^ ^ - — i H + ZntOH]^ hydrogen electrode Ο H φ Zn ^ I I I I I PH I I 10 12 14 I = zone of immunity C = zone of corrosion by dissolution Ρ = zone of passivity [ ZnO ] graphs, a selected number of which, including an atlas [3] on practical cases of corrosion, are mentioned here in Refs [4-16] Reference is also made to the publications of the National Association of Corro sion Engineers (Houston, Texas, USA) and various corrosion insti tutes, associations or study groups in the United Kingdom, Germany, France, the Netherlands, Scandinavia, Belgium, Italy, Spain, the former Czechoslovakia, Hungary, South Africa, Australia and Japan The corrosion of zinc differs markedly from the corrosion (rust ing) of steel In the Pourbaix-diagram of zinc the areas of corrosion by dissolution, the area of passivity (zinc oxide formation) and the area of immunity are defined, when zinc surfaces are exposed to distilled water at 25°C See Fig 1-3 Thus hot-dip galvanized steel, galvanized at 440-465°C will, under these strict circumstances, corrode when the pH-value is above 11 or below In general outdoor practice pH-values of aqueous solutions below 5.5 or above 12.0 will accelerate corrosion of the galvanized steel surface Thus the interfacial reactions of (parts of) the paint film and the zinc (oxide or hydroxide) surfaces will be different from those of paint films on steel surfaces! It should be mentioned here that generally the volume of zinc corrosion products is slightly higher than the volume of zinc from which these corrosion products have been formed Fig 1-3 Potential-pH diagram zinc at in distilled water 25°C for Chapter I It has been shown that duplex systems will provide high anticorrosion protection, as will be discussed in the following chapters of this book Other constructional materials will also corrode Losses in cor rosion amount to three to four percent of the Gross National Product of most industrialized countries [12-14] Apart from the corrosion losses and the economic and ecological consequences involved, it should be mentioned that later repair work and reconditioning not usually restore the original protective values of the coating system — mainly because the circumstances of reconditioning (local climate, type of structure, surroundings, plant production scheme, etc.) are often not the optimum for reconditioning [15] In all cases where the selection of an anticorrosive material is impossible for both technical and economic reasons, the use of pro tective coating systems has been a universal practice The general characteristics of such paint systems are: (i) (ii) (iii) (iv) (v) (vi) when applied to steel surfaces free from rust and impurities they must yield adequate protection for periods between seven and twelve years before rust starts to form; they must sufficiently retard the diffusion of moisture, oxygen, water and pollutants; they must remain active at the interface steel/coating; they must be acceptable from an ecological point of view; they must be able to be applied under the local environmental laws; they must be easy to recondition and repair during and after their period of protection A very wide range of both organic and inorganic coatings is available for the protection of steel surfaces, although it must be borne in mind that a number of paint and bituminous products today are subject to strict environmental and safety laws Modern anticorrosive paint systems are nowadays largely applied in air-conditioned build ings in order to obtain optimum application conditions, as well as drying and hardening parameters Airless spraying, electrostatic spraying, roller coatings, fluidized bed coating, hot spraying, applica tion by cataphoresis, etc., have been developed for application proc esses on meticulously pretreated metal surfaces Of the aforementioned coating applications, continuous hot-dip galvanized steel and related galvannealed sheet plus one or more organic coatings (mainly stoving enamels) are increasingly used in the automotive industry as well as in fabrication of "white goods", where lifetime-issues of 5-10 years are nowadays required Their use for buildings, bridges, offshore platforms, transmission towers, street furniture etc requires lifetimes between 20 and 50 years Duplex systems can provide such long-range protection, as described and illustrated in Chapter X (case histories) 196 Chapter Fig X-42 The monumental the International The Hague Court hot-dip galvanized alkyd is no in was and painted paint sweep-blasting of of Justice (the Netherlands) a black After gate with after the zinc approximately Χ surface 20 years, there corrosion (t) Entrance gate to the International Court of Justice, The Hague (the Netherlands) The monumental entrance gate to the International Court of Justice in The Hague was galvanized and, after sweep-blasting as a surface pretreatment, was painted with a black alkyd paint After some twenty years of weathering in a marine/industrial atmosphere, no rust has formed Case histories and other practical results with duplex systems (u) Bergpolder apartments in Rotterdam (the Netherlands) This steel structure in Rotterdam was built in 1934 and is exposed to a severely polluted atmosphere (see Figs X-43 to X-45) The Bergpolder apartments in Rotterdam were the first high-rise residential flats in the Netherlands They were built in 1933 as a mixed steel/concrete construction Practically all the steelwork has been hot-dip galvanized and the larger part has been painted afterwards The building — now being renovated — has been exposed to a severe moist industrial climate since the late forties, yet the duplex system and also the zinc layer system have adequately protected the steel against rusting, as Shown in FigS X-43-^5 197 Fig.x-43 General view of a Practically all steelwork has been hot-dip galvanized and most of it has been painted with an alkyd resin-based paint, pigmented with micaceous iron oxide After almost 60 years of exposure to a moist and later severely polluted climate, the duplex system and the zinc layer system remain almost fully intact 198 Chapter Fig X-44 View staircases of the apartment of one of in Fig X-43 with on the sheet cladding damage, Detail balustrades of one of thickness topcoat red-brown (see after primer protecting are coating system scraping Fig X-43), paint zinc Total of this duplex Left: rust the the 73μm steel local of the is still adequately the underlying 230 μm system Top left: Underneath the remaining coating building the duplex but no spreading Fig X-45 film, the is off traces visible the of the Χ Case histories and other practical results with duplex systems 199 (v) Gate and the Post Office (PTT) Sorting Centre in Weert (the Netherlands) Although duplex systems with powder coatings not yet offer the long experience of wet paints, several case histories are available nowadays One example is a gate which has been subjected to both corrosion and abrasion for ten years, yet remains fully intact (Fig X-46) It is evident from all these case histories that the synergistic effect of duplex systems has manifested itself under a large variety of applications and under varying climatic conditions The protection offered by the zinc coating system and the paint system is excellent as long as permanent adhesion is obtained by proper pretreatment, paint selection and application Even in circumstances where adhe sion has been diminished and/or severe mechanical damage or ero sion has occurred, duplex systems will often still provide protection Fig X-46 Part gate, of a galvanized powder-coated polyester-based powder Office (PTT) sorting Weert (the Netherlands) years of weathering industrial system (Weert climate, remain a with in a the completely Groep) Post centre at After 10 mildly duplex intact 200 Chapter Χ against rusting of the underlying steel, albeit no longer an optimum protection in such cases References [1] [2] [3] [4] K.-A Van Oeteren: Feuerverzinkung + Beschichtung = Duplex System (Hot-dip galvanizing + coating = duplex system.) Publ Bauverlag GmbH, Wiesbaden, Berlin (1983) Various descrip tions of duplex systems [in German] J.F.H van Eijnsbergen: Various notes on case histories, pub lished in the Dutch/German magazine Thermisch Verzinken/ Feuerverzinken Publ Stichting Doelmatig Verzinken, Sassenheim, the Netherlands and Verband der Deutschen Feuerverzinkungsindustrie, Dusseldorf, Germany (English, Spanish and Italian editions also available since 1991/1993) J.F.H van Eijnsbergen: Conserveringstechnisch onderzoek van de zinklaag en van het duplex-systeem van een aantal hoogspanningsmasten van N.V Electriciteitsbedrijf Zuid-Holland (EZH), te Voorburg (Study of weathered zinc layers and duplex systems on transmission towers of the Southern Holland Elec tricity Company (EZH).) (1990/1991) [in Dutch] F.C Porter: Private communication (1992) 201 Index abrasion resistance, 27 - test, 131 abrasive paper, 156 abrasives, 59 accelerated weathering tests, 13, 117, 137 - cyclic tests, 139 - General Motors Scab Corrosion Test, 141 - Haagen test, 140 - Machutest, 139 - procedures, 138 - QUV apparatus, 140 - salt spray tests, 138 - Weather-O-Meters, 140 acidic degradation products, 160 acrylate resin-based paints, 159, 162 acrylic- and vinyl-based water-borne paints, 161 additives, 86 - cross-linking, 86 - growth of fungi, 86 - paint viscosity, 86 - sedimentation, 86 - skimming, 86 - stability in the can, 86 adhesion, 117 - of air-drying paints to hot-dip galvanized steel surfaces, 76, 77 - bonding forces, 117 - and cohesion tests, 14 - electrostatic forces, 118 - measuring, 87 - mechanical, 118 - promoters, 119, 122, 126 - schematic bonding and diffusing reactions, 123 - thermodynamic or reversible forces, 118 adhesion-promoting agents, 86 adhesion-promoting groups, 128 adhesion testing, 117 - cross-hatch test, 129 - dry and wet adhesion, 128 - impact/adhesion test, 133 - modified Erichsen test, 132 - N-methyl pyrrolidine test, 134 - pull-off dolly, 131 - V-cut test, 130 adhesion values - NMPRT value, 71 - powder cooling, 71 adsorption - and orientation processes, 119 - of polymer chains, 119 - of silane structure, 126 aesthetic effect (colour), 75 air cooling, 32 air-drying binders, 77 alkyd resin-based paints, 159 aluminium, 28 - flakes, 143 - oxide, 47, 53 - paints, 157, 164 aluminium-rich lamellar particles, 52 aluminium-zirconium compounds, 126 American tests, 92 ammonia, 46 amphoteric metals, 45, 137 annealing, 29, 35, 40 - vacuum, 29 anti-blistering agents, 162 application of hot-dip galvanizing, 22 aqueous - dispersion paints, 82, 161 - paints, 78 atmospheric corrosion, 46 Auger electron spectroscopy, 143, 144 Australian paint systems for hot-dip galvanized steel in various atmospheres, 95-97 Australian tests, 94 automotive industry, 4, 34, 54 202 basic functions of duplex systems, beta zinc hydroxide, 155 binder, 76 biological effects of zinc, 41 bismuth chloride, 38 blisters, 161 - and craters in a powder coating, 162 borium fluoride, 60 boundary zone, 117 brittle zeta alloy layer, 159 brown copper deposit, 63 ft-butyl phosphoric acid, 163 calcium orthoplumbate (COP), 88 - calcium zincate, 88 - cementiferous action, 88 - interfacial reactions, 88 carbonate scale, 157 case histories, 10, 167 - airport landing lights, 194 - apartments, 197 - catenary of railway lines, 178 - cheese racks, 193 - chemical engineering plant, 189 - chimney, 187 - climbing frames, 195 - Colorgalv system, 191 - dam wall, 180 - floodlight mast, 186 - gates, 196, 199 - lifeboat, 183 - locks, 179 - long-term weathering tests, 174 - pilot vessels, 184 - restaurant, 190 - roof panels, 181 - roof tiles, 188 - school fac^ade, 192 - transmission towers, 167 - wind tunnel, 186 cataphoretic primer, 114 cathodic depolarization, 139 cathodic protection, 36, 40, 54 centrifuge-galvanizing plant, 31 cerium-lanthanum alloy, 52 chelates, 122, 124 Index chemical conversion coating, 59 chemical treatments - chromating, 60 - light chromate rinsing, 60 - phosphating, 60 chlorinated rubber primers, 159 chromate coatings, 63 chromate layer, 63 - self-healing, 64 chromate treatment, 34, 61 chromating, 60 - depolarizing reaction, 63 - etching reaction, 63 - film forming reaction, 63 - solutions, 63 cleaning hot-dip galvanized surfaces - application, 59 - cleaning agents, 59 - contaminants, 59 - grit-sweeping, 59 - high-pressure jetting, 59 - vapour blasting, 59 cleaning weathered duplex systems, 59 climate, 48 coating micrographs, 35 coating thickness, 24-26, 48 Coating Quadrant, 89 coatings, toxicity of, 41 code of practice, 105 coil coating line, 40 coil coating stoving paint, 83 - main physical and chemical characteristics, 83 coil coatings, 81, 102 - main characteristics of nine types of, 103 - over-coating (reconditioning) of, 104 combigram of duplex systems, comparison of zinc, Galfan and Galvalume - coil galvanized, 36 - corrosion resistance, 36 - edge protection, 36 - Galfan, 36 - Galvalume, 36 - paintability, 36 - white rust resistance, 36 composition of rust, contact angle, 117 203 Index contact potential, 117 contaminants, 57, 155 continuous galvanizing, 34, 39 continuous hot-dip galvanizing, 33 - line for steel coils, 33 continuous-galvanizing, 21 continuous powder coating plant, 111 copper sponges, 156 corona-charging, 112 correct stacking of galvanized and polyester-coated structural parts, 112 corrosion, - losses in, - mechanism of, 121 - propagation of, 122 - resistance, 32, 36, 38, 48 - resistance of galvanized steel, 32 - resistance of hot-dip galvanized steel, 49 - speed, 142 - of zinc surfaces, 3, 137 corrosion rates, 50 - atmospheric attack, 50 - corrosion kinetics, 50 - thermodynamic considerations, 50 corrosion reactions, 47 - duration of wetness, 48 - topochemical nature, 47 covalent bonds, 122, 126 cracked gas, 33 craters in powder coatings, 161 cross-hatch test, 129, 132 crystal orientation, 34 curing temperatures, 120, 121 - nitrites, 58 - organic solvents, 57 - perchloroethylene, 57 - phosphates, 58 - saponification, 58 - trichloroethylene, 57 delaminations, 130, 142 Delta galvanizing, 21 delta layer, 24, 32 delta-1 layer, 50 delta-alloy layer, 24 delta phase, 35 del ta-P test, 101 dipping time, 26 dirt, 155 dispersion paints - acrylate/styrene copolymers, 78 - acrylic resins, 78 - vinyl/acrylate copolymers, 78 dissolution of zinc patina, 46 dolly test, 130 dry and wet adhesion, 127, 129 dry-galvanizing process, 23, 29 drying temperature, 160 duration of protection, 50 duration of wetness, 48 dust, 65, 155 Dutch Galvanizing Institute's test series, 90 - spread of rust, 90 - systems yield good adhesion, 90 - under-creeping of rust, 90 Dutch Normalisation Institute, 134 edge protection, 36 decomposition products, 163 degradation effects with coatings in the atmosphere, 86 degradation of paint films, 140 degreasing of galvanized steel surfaces, 58 degreasing process - carbonates, 58 - chelates, 58 - degreasing solutions, 57 - dispersion activity, 58 - emulsifying and chelating agents, 57 - Fettrot BB or Ceresrot solution, 57 effects of galvanizing temperature and dipping time, 29 electrochemical impedance spectroscopy, 142 electrogalvanized steel, 126 electron spin resonance spectroscopy, 145 embrittlement, 32 empirical formula of duplex systems, emulsifying agents, 161 encrustation, 51 environmental effects of zinc, 41 epoxy/coal-tar paint, 161 epoxy coatings, 101 204 epoxy paints, 78 - amines, 79 - cyclic aliphatic amines - epoxy resin/hardener ratio, 81 - hardening agents, 79 - polyamides, 79 epoxy powder, 70 epoxy resin-based paints, 159, 160 Erichsen instrument, 132 Erichsen test, 131, 132 evaluating duplex systems on test panels, 140 extenders, 83, see also pigments and extenders falling ball test, 132 faults - during application, 154 - of duplex systems, 163, 165 film formation, 84 flaking, 160, 161 flexibility, 81 fluidized-bed applications of powders, 114 - adhesive primer, 114 - fluidized bed coatings, 114 - fluidized bed tank, 114 fluorides, 60 flux, 24, 65 fluxing, 153 fluxing powder, 154 Fourier transform infrared spectroscopy, 144 Galfan, 36-39, 101, 102 Galfan sheet, 52 Galvalume, 8, 36, 39, 40, 53, 102, 105 - Algafort, 36, 53 - Aluzinc, 36, 53 - Aluzink, 36, 53 - Zalutite, 36, 53 - Zincalit, 36, 53 galvanizability graph, 27 galvanized steel surfaces - degreasing, 58 galvanized steel - corrosion resistance of, 32 galvanizing silicon-killed steels, 50 galvannealed sheet, 4, 35, 54, 102, 130 - in the automotive industry, 54 Index - cathodic protection, 54 - deep-drawing, 54 - galvannealed coatings in Japan, 54 - powder of flake-like peeling, 54 galvannealing, 35, 39 gaseous ammonia, 33 general characteristics of paint systems, general galvanizing process, 23 general phosphating reaction - diphosphates, 61 - hopeite, 62 - monophosphates, 61 - phosphophyllite, 62 - phosphoric acid, 61 - triphosphates, 61 General Motors Scab Corrosion Test, 65, 120, 141 Glow Discharge Optical Spectroscopy, 148 greasy surfaces, 159 gritty surfaces, 159 Haagen (accelerated) test, 100, 101, 141 hammer test, 130 hardening temperature, 160 health, 41 hexagonal zinc crystals, 28, 34, 40 high-pressure water jets, 60 high-temperature galvanizing, 39 history of duplex systems, 10 hot-dip galvanized steel - adhesion of air-drying paints to, 76, 77 - corrosion resistance of, 49 - surface defects in, 153, 154 - weathering of, 22, 52 hot-dip galvanizing, 21 - application of, 22 - continuous-galvanizing, 21 - Delta galvanizing, 21 - job-galvanizing, 21 - main characteristics of, 39 hydrochloric acid, 24 hydrogen bonds, 117 hydrolysable solvents, 160, 163 hydroxides, 65 hygroscopic zinc phosphate, 159 205 Index immersion times, 28 impedance, 142 impurities, 57 influence of pigment volume concentration, 85 influence of sulphur dioxide, 49 influence of type of steel after hot-dip galvanizing, Ί - adhesion, 25 - coating thickness, 25 - colour, 25 - silicon percentages, 25 infrared spectroscopy, 144 infrared thermography, 146 inhibited sulfamine acid, 58 interaction energy, 117 interface, 118 interface active primer, 124 interfacial reactions, interfacial volume, 118 interfacial zone, 117 intergranular corrosion, 53 intermetallic iron-aluminium-zinc-silicon layer, 53 intermetallic layer, 36 intermetallics, 53 intermolecular forces, 117 internal (cohesional) stresses, 163 ion sputtering spectroscopy, 144 iron particles, 50 job galvanizing, 21, 39 - plant, 30 killed steel, 27 - unkilled steel, 27 lamellar and non-lamellar pigments, 85 lead, 28 - layer of molten, 28 light blasting, 59 light chromate rinsing, 60 light sweep-blasting, 154 liquid primer (Maxpro), 108 Lithoform, 62 losses in corrosion, magnesium, 53 main characteristic of duplex systems, 75 main characteristics of the hot-dip galvanizing process, 39 - continuous galvanizing, 39 - Galfan, 39 - Galvalume, 39 - galvannealing, 39 - high temperature galvanizing, 39 - job (general) galvanizing, 39 Maxpro, 108, 124 measuring adhesion, 87 mechanical bonds, 117 mechanical pretreatments - sweep-blasting, 65 - water blast, 65 mechanical treatments, 59, 71 mechanism of corrosion, 121 melamine/alkyd, 163 metallizing, 164 metals, amphoteric, 45 /V-methyl pyrrolidine (NMP), 120, 133 microclimate, 48, 138, 141 microcracking, 27 micrograph - of Galvalume, 37 - of galvanized steel, 27, 28 microhardness, 27 migration of plasticizers, 160 mineral oil, 63 mischmetal, 52 Mossbauer spectroscopy, 146 nickel, 28, 48, 50 nitrogen oxides, 46 NMPRT adhesion test, 65, 120 nuclear magnetic resonance, 145 nucleation agents - diammonium phosphate, 53 zinc dust, 53 oil, 155 one-side coatings, 34 organofunctional silanes, 124 organosilanes, 127 orientation of hexagonal zinc crystals, 51 - 0001-base plane, 51 orientation of zinc crystals, 29 206 outdoor testing, 92, 137, 139 outside-only galvanizing, 32 over-coating (reconditioning) of coil coatings, 104 paint fundamentals, 75 paint ingredients - additives, 76 - binder or vehicle, 76 - pigments and extenders, 76 - volatile products (solvents, thinners), 76 paint products - epoxy resins, 100 - polyurethane, 100 - vinylchloride/acrylate and vinylchloride/isobutylether combinations, 100 paint systems - general characteristics of, paintability, 36 paints - acrylate and methacrylate resins, 89 - chlorinate rubber paint products, 89 - cyclicized rubber, 89 - epoxy resins, 89 - polyester resins, 89 - polyurethane resins, 89 - type of, 76 - vinyl resin, 89 - wrong selection of, 154, 159 passive aluminium-rich phase, 40 peeling, 159 permeability, 80 - coefficients, 80 - of water (vapour) and oxygen, 80 pH values, phase - compact delta-1,31 - delta, 35 - eta, 31 - gamma, 31 - gamma-1,31 - pallisade delta-1, 31 phosphate cleaners - morphology of the phosphate layer, 58 phosphating, 60 phosphor, 26 phosphoric acid, 58, 163 Index photon electron emission (PEE), 57 pigment/volume ratio, 76 pigments and extenders, 83 - aluminium pigment, 84 - lamellar structure, 83 - permeability, 83 - pigment volume concentration, 84 - pigment volume ratio, 83 pinholing, 162 pinpoints of rust, 33, 156 polar (intermolecular) bonds, 117 polyester/epoxy types of powder, 112 polyester powders, 40, 70, 112 polyester-based powder coatings, 11, 162 polyethylene oxide, 162 polyurethane-based liquid paints, 162 polyurethanes, 79 possible failures, 14 pot life, 79 potential-pH diagram, Pourbaix-diagram, - immunity, - passivity, powder coatings, 78 - anti-blistering agents, 110 - blisters in, 109, 162 - craters in, 161, 162 - chemical resistance of, 106, 107 - curing, 111 - curing temperatures, 111 - degassing, 110 - heating of aluminium, 109 - pinholing, 110, 111 - polyester-based, 162 - polyethylene oxide, 110 - pros and cons, 105 - reactivity, 106 - scheme for hot-dip galvanized steel, 113 - sprayed on aluminium, 109 pretreatment faults, 154, 158 pretreatments, 57 pretreatments for galvanized steel, 69 - chromating, 69 - cold etching (phosphating), 69 - galvannealing, 69 - hot phosphating, 69 207 Index - light blasting or sweeping, 69 - outdoor weathering, 69 - rubbing or scouring with abrasive paper, 69 prevention, 14 primary and secondary valence forces, 117 principal advantages of duplex systems, 18 propagation of corrosion, 122 Raman spectroscopy, 145 reaction products, 47 - products, aluminium oxide, 47 - zinc bisulphate, 47 - zinc carbonate, 47 - zinc chloride, 47 - zinc hydrocarbonate, 47 - Σ and β-zinc hydroxide, 47 - zinc oxide, 47 - zinc oxychloride, 47 - zinc patina, 47 - zinc sulphate, 47 - zinc sulphide, 47 reactions during phosphating - hopeite, 60 - manganese and nickel compounds, 60 - nitrites, 60 - orthophosphoric acid, 60 - oxidizing agents, 60 - peroxides, 60 - phosphophyllite, 60 - zinc phosphate, 60 reactive steel surfaces, 32 reactivity of powder coatings, 106 reconditioning - of damages areas, 164 - paint, 103 - procedures, reliability, - reliability factor R , - values, repair, 14 roller process, 102 roughness profile, 72 rust, - composition of, - goethite, - iron sulphate, - lepidocrocite, - magnetite, - pinpoints of, 33, 156 - salt (NaCl) encrustations, - spread of, 90 - stains, 51 - under-creeping of, 90 rusting processes, 137 salt spray tests, 13, 139 scanning electron microscopy, 145 scanning Kelvinprobe, 146 scanning tunnelling microscopy, 146 secondary ion mass spectroscopy, 29, 143 semi-killed steel, 26 sequestering agents, 161 silane coupling agents, 127 silanes, 119, 124, 126, 126 silicate/SAAPS pretreatment, 126 silicate solution, 126 silicates, 159 silicon, 26, 29 - surface enrichment by, 29 silicon fluoride, 60 silicon percentages, 26 silicon-killed steels, 26, 29 skimming, 153 skin passing, 33, 40, 51 skin-pass treatment, 103 slow withdrawal for zinc bath, 153 sodium molybdate, 64 sodium silicate solution - hydrolysable groups, 65 - silanes, 65 - silanol groups, 65 - silicate/silane post rinses, 65 - silicate/silane process, 65 - substitute silane compounds, 65 solders, 164, 165 solvent retention, 162 solvent-free epoxies, 79 South African tests - conclusions, 94 - duplex systems exposed to a marine atmosphere, 94, 98 - duplex systems in mine shafts, 94, 99 208 - exposure of duplex systems, 94 - impact resistance, 99 spangle size, 53 spatter, 155 special fluxes, 38 specifications for duplex systems, 105 stanchions, 183 steel, - alloying elements, 29 - annual world production, - corrosion protection, - recycling percentage of, Stichting Doelmatig Verzinken, 134 stoving paints, 82 see also thermohardening or stoving paints - paint film characteristics, 82 stoving temperatures, 78 stresses, 24 sulphur dioxide, influence of, 49 Supergalva alloy, 38 Superzinc, 37 surface analysis, 117, 137 - auger electron spectroscopy, 143, 144 - electrochemical impedance spectroscopy, 142 - electron spin resonance spectroscopy, 145 - Fourier transform infrared spectroscopy, 144 - Glow Discharge Optical Spectroscopy, 148 - infrared spectroscopy, 144 - infrared thermography, 146 - ion sputtering spectroscopy, 144 - Mossbauer spectroscopy, 146 - nuclear magnetic resonance, 145 - scanning electron microscopy, 145 - scanning Kelvinprobe, 146 - scanning tunnelling microscopy, 146 - secondary ion mass spectroscopy, 143 - X-ray micro analysis, 148 - X-ray photo electron spectroscopy, 143 surface defects in hot-dip galvanized steel, 153, 154 surface enrichment by silicon, 29 surface pretreatments - hydrosilicon fluoric acid, 64 - nitrite accelerators, 64 - tri-cation-phosphate solutions, 64 sweep-blasting, 65, 67, 68, 101, 159 - abrasives, 67 Index - air pressure, 68 - aluminium oxide (corundum), 67 - distance, 68 - light, 154 - surface profile, 68 - Vasilgrit Z, 67 sweeping, 60 - of hot-dip galvanized steel surfaces, 68 synergistic effect, 7, 117, 199 - synergistic factor, T-Wash, 62 tertiary zinc-aluminium-nickel alloy, 51 thermal aluminium oxides, 39 thermal coefficient of expansion, 27 thermohardening or stoving paints, 78 - acrylic resins, 78 - melamine, 78 - non-drying oil modified alkyl resin combinations, 78 - plasticized phenol or cresol resins, 78 - polyester resins, 78 - silicone alkyds, 78 - ureaformaldehyde, 78 thickness trajectory, 66, 67 tin, 28 tin chloride, 38 titanate, 127 titanium phosphate, 61 TNO Coatings Centre tests, 89 - anti-corrosive pigment, 92 - dry adhesion, 92 - new galvanized sweep-blasted panels, 92 - non-weathered zinc surfaces, 92 - panels preweathered for six months and twenty months, 92 - sweeping, 92 - wet adhesion, 92 topography of the steel surface, 29 total layer composition, 24 toxicity of coatings, 41 transmission tower lines, 100 tri-cation systems - manganese-nickel-iron phosphates, 62 tri-cation-phosphating process, 62, 64 tribo-spraying powders, 111 209 Index - Faraday cage, 111 - tribo-electrostatic spraying gun, 111 trivalent chromate solutions, 64 two-component paints, 78 type of paint (vehicle basis), 76 ultraviolet rays, 163 ureaformaldehyde/alkyd, 163 use of duplex systems, 14 V-cut test, 130 Vacublast apparatus, 156, 157 vacuum annealing, 29 Van der Waals forces, 117 Vasilgrit, 68 vehicle, 76 Vereniging van Spuit- en Moffelbedrijven, 134 volatile organic compounds (VOC), 78, 137 volatile products, 80 volatile products - hydrolysable solvents, 85 volume of zinc corrosion products, wash primers, 87, 94 - interfacial reactions, 88 - one-component, 88 water absorption and water permeability, 81 water jetting, 164 water quenching, 29 water-blast systems, 59 wear-resistance test, 131 weather resistance, 137 weathered zinc surface, 48 weathering - of duplex systems, 87 - of painted constructional steel and hot-dip galvanized steel, 22 weathering phases of hot-dip galvanized steel, 52 welding slag, 144 wet galvanizing, 29 wet-blasting methods - glass granulate, 59 - Vasilgrit Z, 59 wetting angle, 118 white goods, 4, 34 white rust, , , 155 white - formation, 156 resistance, 36 rust inhibitors, 45 8-hydroxyquinoline, 45 polyacrylic acid, 45 polyvinylpyrrolidone, 48 zinc phosphonate, 45 X-ray analysis, 145 X-ray micro analysis, 148 X-ray photo electron spectroscopy, 143 youth period, 138 zeta layer, 28 zinc - environmental and biological effects of, 41 zinc ammonium chloride, 38 zinc bisulphate, 47 zinc carbonate, 47 zinc chloride, 47 zinc crystals - hexagonal, 34, 40 - orientation of, 29, 51 zinc formate, 160 zinc hydrocarbonate, 47 zinc hydrosulphate, 46 zinc, impurities on, 57 zinc oxide, 47 zinc oxychloride, 47 zinc patina, 45, 47 zinc phosphate, 62 zinc phosphate crystals, 60 zinc recycling, zinc sulphate, 46, 47 zinc sulphide, 47 zinc surfaces, 45 - carbonation, 45 corrosion of, 137 dissolution of the zinc patina, 46 encrustation, 46 fluxing agents hydration, 45 hydrolysis, 46 industrial atmosphere, 46 oxidation, 45 210 - reaction with aluminium, 46 - salty air, 46 - weathered, 48 zinc(oxy)chlorides, 51 zinc-rich primer - based on epoxy resin vehicle, 157 - based on partially hydrolysed silicate binder, 157 - inorganic (silicate), 155 - organic (silicate), 155 Index zinc-aluminium alloys, 53 zinc-aluminium surfaces, alkaline degreasing solutions, 58 zinc-ammonium chloride, 24 zinc-iron alloy layers, 28, 40, 50 zinc-nickel alloy, 40 zinc-nitrogen compounds, 46 zincates (ammonium zincate), 46 zirconium, 126 [...]... of duplex systems is difficult to trace in detail It is evident that duplex systems were in use before World War II, as can be seen from a number of case histories given in Chapter X However, it was in the early fifties when a more systematic study of duplex systems began At that time, the name "duplex systems" was given to the combination of hot-dip galvanized steel and organic coatings Duplex systems: ... Examples of duplex systems are the photographs in Figs II-4— 11-14 The principal advantages of duplex systems are given in Fig 11-15 References [1] J.F.H van Eijnsbergen: Het verven van thermisch verzinkt staal (Painting of hot-dip galvanized steel.) Uitgave Stichting Doelmatig Verzinken, The Hague (1967) [in Dutch] [2] J.F.H van Eijnsbergen: Twenty years of duplex systems — galvanizing plus painting... protection through duplex systems Lecture and discussion meeting.) Gemein schaftsausschuB Verzinken (GAV), Dusseldorf (1987) [in Ger man] [15] Geholit + Wiemer GmbH (1988), Internationales Duplex- Fo rum, Karlsruhe (International duplex forum.) [in German] (a) H.-J Bottcher, Duplexsysteme aus der Sicht des Verzinkers (Duplex systems from the galvanizer's point of view.) (b) M Wilk, Duplexsysteme aus... point of view.) (b) M Wilk, Duplexsysteme aus der Sicht des Auftraggebers (Duplex systems from the client's point of view.) (c) H Tilmans, Duplexsysteme aus der Sicht des Beschichtungsunternehmens (Duplex systems from the coater's point of view.) (d) R Schmidt, Duplexsysteme aus der Sicht des Beschichtungsstoff-Herstellers (Duplex systems from the paint manu facturer's point of view.) (e) R Schmidt, Ubersicht... und Eigenschaften (Overview of coating materials for duplex systems: their selection and properties.) (f) W Wolff, Duplexsysteme im Korrosionsschutz ab Werk (Duplex systems in corrosion protection ex factory.) (g) J.F.H van Eijnsbergen, Erfahrungen mit Duplexsystemen aus internationaler Sicht auf Zn- und Zn-Al-Oberflachen (Experience with duplex systems from an international point of view on Zn- and... durability factors for zmc pa 8 Chapter Fig 11-1 Combigram of duplex systems a: industrial atmosphere; atmosphere; c: marine d: rural formula for Duplex = + £*paint/- systems: The ciphers of protection duplex systems Example: To hot-dip steel with 70μm paint coating atmosphere, type to bare approximately part of steel coating will, in offer 3 The duplex steel against 18 years zinc 9 of atmosphere, protection... appli cation Duplex systems have been shown to have relatively high R values when compared with paint systems (applied on blasted or hand-brushed steel surfaces) and with hot-dip galvanizing (see Fig II-2) Coating system Hot-dip galvanizing Zinc-rich primer on Sa2^ blasted steel surface Classical paint system (4 coats) on manually derusted steel surface Duplex system (hot-dip galvanized steel plus primer... are known under the general name of duplex systems* (see Chapter II, Refs 1-15) Optimal results with duplex systems are obtained when, after hot-dip galvanizing, the zinc surface is immediately painted, as will be described in Chapters IV, V and VI Although painting may also be carried out at a later date on weathered zinc surfaces, practice has shown that such duplex systems often do not offer the ultimate... applying duplex systems on their own premises in specially equipped coating plants Fig 11-9 Duplex pedestrian (GAA) bridge system in on a Australia 15 Duplex systems: definition, function, history and general use Fig 11-10 refinery hot-dip galvanized, structure system Railways of a large difficult partly partly (upper to reach) duplex (SDV) Fig 11-11 overhead Flarestack in the Netherlands; Duplex catenary... products (structural parts, cars, white goods, etc.) replacing the old and, for duplex systems particularly, unreliable salt spray tests have made a system kindergarten on figures (SDV) 14 Chapter Ιί better insight into the behaviour and protective value of duplex systems possible Surveys of modern testing methods for duplex systems, in which adhesion/cohesion tests play a prominent role, are briefly