Failure Analysis of Paints and Coatings Revised Edition Dwight G. Weldon Weldon Laboratories, Inc, Imperial, PA, USA A John Wiley & Sons, Ltd., Publication
Failure Analysis of Paints and Coatings Revised Edition
Failure Analysis of Paints and Coatings Revised Edition Dwight G. Weldon Weldon Laboratories, Inc, Imperial, PA, USA A John Wiley & Sons, Ltd., Publication
This edition first published 2009 2009 John Wiley and Sons, Ltd Registered offi ce John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www. wiley.com. The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular purpose. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for every situation. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom. Library of Congress Cataloging-in-Publication Data Weldon, Dwight G. Failure analysis of paints and coatings / Dwight G. Weldon. Rev. ed. p. cm. Includes bibliographical references and index. ISBN 978-0-470-69753-5 (pbk.) 1. Paint Testing. 2. Coatings Testing. I. Title. TP936.5.W45 2009 667.90287 dc22 2009005620 A catalogue record for this book is available from the British Library. ISBN: 978-0-470-69753-5 (Cloth) Set in 10 on 12 pt Times by SNP Best-set Typesetter Ltd., Hong Kong Printed and bound in Great Britain by TJ International, Padstow, Cornwall
To my son Andy, who can still make me smile.
Contents Preface to the Revised Edition Preface to the First Edition Acknowledgements xiii xv xvii 1 General Principles of Coating Formulation 1 1.1 Introduction 1 1.2 Binders 2 1.3 Pigments 4 1.4 Solvents 5 1.5 Additives 5 1.6 Formulation Concepts: Pigment-to-Binder Ratio 6 1.7 Formulation Concepts: Pigment-Volume Concentration 6 1.8 Formulation Concepts: Density, Weight Solids and Volume Solids 7 References 8 2 Why Coatings Work and Why They Fail 9 2.1 Why Coatings Work 9 2.1.1 Adhesion 9 2.1.2 Wetting 10 2.1.3 Surface Preparation 14 2.1.4 Cohesive Strength 23 2.1.5 Permeability 23 2.2 Why Coatings Fail 24 2.2.1 Mechanical Stress 25 2.2.2 Internal Stress 29 2.2.3 Chemical Attack 31 2.2.4 Weathering Stress 33
viii CONTENTS 2.2.5 Osmotic Blistering 34 2.2.6 Electroendosmotic Blistering 35 References 36 3 Pigments 39 3.1 Inorganic Pigments 39 3.1.1 Inorganic Colour Pigments White 39 3.1.2 Inorganic Colour Pigments Yellow 40 3.1.3 Inorganic Colour Pigments Orange 40 3.1.4 Inorganic Colour Pigments Red 41 3.1.5 Inorganic Colour Pigments Blue 41 3.1.6 Inorganic Colour Pigments Green 41 3.2 Extender Pigments 41 3.2.l Silica/Silicates 42 3.2.2 Calcium Carbonate 42 3.2.3 Barytes 43 3.3 Corrosion-Resistant Pigments 43 3.4 Organic Pigments 46 3.4.1 Organic Red Pigments 47 3.4.2 Organic Yellow Pigments 48 3.4.3 Organic Blue Pigments 49 3.4.4 Organic Green Pigments 50 References 50 4 Additives and Solvents 51 4.1 Additives 51 4.1.1 Anti-settling Agents 51 4.1.2 Viscosity Modifiers 52 4.1.3 Surfactants and Emulsifying Agents 53 4.1.4 De-foaming and Anti-foaming Agents 54 4.1.5 Driers 54 4.1.6 Plasticizers 54 4.1.7 Ultraviolet Stabilizers 55 4.1.8 Anti-skinning Agents 55 4.1.9 Biocides 56 4.1.10 Flow-Modifying Agents 56 4.2 Solvents 57 References 64 5 Coating Types and Common Failure Modes 65 5.1 Natural Resins and Oils 65 5.1.1 Natural Resins 66 5.1.2 Oils 68
CONTENTS ix 5.2 Alkyds and Epoxy Esters 70 5.2.1 Alkyds 70 5.2.2 Epoxy Esters 74 5.3 Epoxies 75 5.3.1 Amine and Amide Curing Agents for Epoxy Resins 76 5.3.2 Epoxy Failure Modes 80 5.4 Modified Epoxies 84 5.4.1 Acrylic Epoxies 84 5.4.2 Coal Tar Epoxies 85 5.4.3 Epoxy Phenolics 85 5.5 Phenolics 86 5.5.1 Resole Phenolics 86 5.5.2 Novolac Phenolics 87 5.5.3 Phenolic Failure Modes 87 5.6 Amino Resins 88 5.7 Acrylics 90 5.7.1 Solution Acrylics 91 5.7.2 Acrylic Latex Coatings 92 5.7.3 Thermoset Acrylics 95 5.8 Polyesters 96 5.8.1 Saturated Polyesters 97 5.8.2 Unsaturated Polyesters 100 5.9 Polyurethanes 101 5.9.1 Two-Component Polyisocyanate/Polyol Coatings 103 5.9.2 Urealkyds 106 5.9.3 Moisture-Cured Polyurethanes 107 5.9.4 Polyurethane Lacquers and Dispersions 108 5.9.5 Two-Component Water-Borne Polyurethanes 108 5.10 Vinyls 109 5.10.1 Solution Vinyls 109 5.10.2 Plastisols and Organosols 110 5.10.3 Vinyl Fluorides 110 5.10.4 Poly(vinyl butyral) 111 5.10.5 Vinyl Latexes 111 5.11 Bituminous Coatings 112 5.12 Inorganic and Silicone-Modified Coatings 114 5.12.1 Silicone Coatings 114 5.12.2 Silicate Coatings 116 5.12.3 Polysiloxane Coatings 118 5.13 Polyureas 120 5.13.1 Polyaspartic Polyurea Coatings 121 5.14 Powder Coatings 122 References 124
x CONTENTS 6 Application-Related Problems 125 6.1 Brush and Roller 125 6.2 Spray Applications 126 6.2.1 Air (Conventional) Spray 126 6.2.2 Airless Spray 126 6.2.3 Plural Spray 127 6.2.4 Electrostatic Spray 127 6.3 Flow Coating 127 6.4 Roll Coating 128 6.5 Powder Coating 128 6.6 Coating Failures Related to Application Problems 129 References 134 7 Field Methods 135 8 Analytical Methods 141 8.1 Light Microscopy 141 8.2 Infrared Spectroscopy 152 8.2.1 Theory 152 8.2.2 Instrumentation 166 8.2.3 Sample Handling 169 8.2.4 Applications 177 8.3 Gas Chromatography (GC) 202 8.3.1 Theory of GC 202 8.3.2 Instrumentation 208 8.3.3 Pyrolysis-GC 216 8.3.4 Application of GC 217 8.4 Gel Permeation Chromatography (GPC) 221 8.4.1 Theory 222 8.4.2 Instrumentation 226 8.4.3 Applications 227 8.5 Ion Chromatography 232 8.5.1 Theory 232 8.5.2 Applications 237 8.6 Scanning Electron Microscopy 238 8.6.1 Imaging Theory 239 8.6.2 Elemental Analysis by X-ray Spectroscopy 241 8.6.3 Sample Preparation 244 8.6.4 Applications of SEM-EDS 244 8.7 Differential Scanning Calorimetry (DSC) 247 8.7.1 Theory 247 8.7.2 Calibration and Sample Preparation 250 8.7.3 Applications of DSC 252 8.8 Miscellaneous Methods of Analysis 258 References 259
CONTENTS xi 9 Physical Methods 261 9.1 Adhesion 261 9.2 Flexibility and Impact Resistance 263 9.3 Solvent Resistance 265 9.4 Weathering Resistance 265 9.5 Chemical Resistance 266 9.6 Freeze Thaw 269 9.7 Application Variables 269 References 273 10 Examples of Coating Failures 275 10.1 Urethane Topcoat Disbonding from Epoxy 275 10.2 Blistering of an Epoxy Tank Coating 279 10.3 Cracking and Delamination of Epoxy Coating Systems on Masonry Walls 282 10.4 Discolouration of Coil-Coated Aluminium Siding 285 10.5 Discolouration and Delamination of Plastisol 288 10.6 Delamination of Floor Coating 293 10.7 Delamination of Dry-Fall Alkyd 296 10.8 Coal Tar Epoxy Failure 300 10.9 Splitting of Inorganic Zinc-Rich Primer 304 10.10 Defects on Electro-Coated Panels 309 10.11 Failure of Coated Light Poles 309 10.12 Blistering of Coating on Concrete Floor, Number 1 314 10.13 Blistering of Coating on Concrete Floor, Number 2 318 10.14 Peeling of Paint from Metal Chairs 322 10.15 Failure of Railroad Car Liner 327 10.16 Failure of Calcium Sulfonate Modified Alkyd Topcoat from a Bridge 331 10.17 Discolouration of Furniture Lacquer 333 10.18 Failure of Tank Car Lining 337 References 345 11 The Repair of Coating Failures 347 Index 351
Preface to the Revised Edition It has been over 8 years since the first edition of Failure Analysis of Paints and Coatings was published. During this period, many coating types have remained the same, and a few new ones have been introduced, or at least have been more heavily marketed. Advances have been made in surface preparation technology, and more opportunities for training and education have been made available than ever before. However, in spite of all of this, the coatings industry still experiences its fair share of failures. A coating failure does not just involve the cost of some paint. Repair of an existing structure can be extremely expensive, perhaps even entailing lost production time if the facility has to be shut down for repairs. If a coating lining a process vessel or a railroad tank car fails, large amounts of product may become unmarketable and may have to be disposed of. Reputations can be damaged. The cost of a paint failure is seldom cheap. The first edition of this book introduced some basic concepts in paint formulation and chemistry. This has been updated in the second edition to include some additional types of coatings, such as polyureas, polysiloxanes and powder coatings. Some additional discussion has been included concerning surface preparation, the mechanism of blistering and the chemistry of amine blush. Analytical techniques such as gas chromatography mass spectroscopy and differential scanning calorimetry have been discussed in more detail. However, as with the first edition, the subjects of coatings chemistry and analytical chemistry are presented at the introductory level. Although essential to conducting a failure analysis, many thorough texts already exist on these subjects. As pointed out in the preface to the first edition, the failure analysis of paints and coatings is all about problem solving. Problem solving is a difficult subject to teach, and probably relies on curiosity and experience more than anything else. Therefore, in addition to the basics of coatings science and analytical chemistry, which form the foundation upon which curiosity and experience can build, this book contains numerous practical examples of solving real - world coating failures. Indeed, the biggest difference between the first and second editions is