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Corrosion and Corrosion Protection Handbook: Second Edition, Revised and Expanded, edited by Philip A.Schweitzer 2.. Corrosion Resistance Tables: Metals, Nonmetals, Coatings, Mortars, Pl

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Corrosion of Ceramic and Composite

Materials

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CORROSION TECHNOLOGY

Editor

Philip A.Schweitzer, P.E.

Consultant York, Pennsylvania

1 Corrosion and Corrosion Protection Handbook: Second Edition, Revised and Expanded, edited by Philip A.Schweitzer

2 Corrosion Resistant Coatings Technology, Ichiro Suzuki

3 Corrosion Resistance of Elastomers, Philip A.Schweitzer

4 Corrosion Resistance Tables: Metals, Nonmetals, Coatings, Mortars, Plastics, Elastomers and Linings, and Fabrics: Third Edition, Revised and Expanded (Parts A and B), Philip

A.Schweitzer

5 Corrosion-Resistant Piping Systems, Philip A.Schweitzer

6 Corrosion Resistance of Zinc and Zinc Alloys, Frank C.Porter

7 Corrosion of Ceramics, Ronald A.McCauley

8 Corrosion Mechanisms in Theory and Practice, edited by

P.Marcus and J.Oudar

9 Corrosion Resistance of Stainless Steels, C.P.Dillon

10 Corrosion Resistance Tables: Metals, Nonmetals, Coatings, Mortars, Plastics, Elastomers and Linings, and Fabrics: Fourth Edition, Revised and Expanded (Parts A, B, and C), Philip

A.Schweitzer

11 Corrosion Engineering Handbook, edited by Philip A.Schweitzer

12 Atmospheric Degradation and Corrosion Control, Philip A.

16 Corrosion-Resistant Linings and Coatings, Philip A.Schweitzer

17 Corrosion Mechanisms in Theory and Practice: Second Edition, Revised and Expanded, edited by Philippe Marcus

18 Electrochemical Techniques in Corrosion Science and Engineering, Robert G.Kelly, John R.Scully, David W.Shoesmith,

and Rudolph G.Buchheit

19 Metallic Materials: Physical, Mechanical, and Corrosion Properties, Philip A.Schweitzer

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20 Encyclopedia of Corrosion Technology: Second Edition, Revised and Expanded, Philip A.Schweitzer

21 Corrosion Resistance Tables: Metals, Nonmetals, Coatings, Mortars, Plastics, Elastomers and Linings, and Fabrics: Fifth Edition, Revised and Expanded (Parts A, B, C, and D), Philip A.

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Corrosion of Ceramic and Composite

Materials

Second Edition

Ronald A.McCauley

Rutgers University Piscataway, New Jersey, U.S.A.

M ARCEL D EKKER , I NC N EW Y ORK • B ASEL

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Transferred to Digital Printing 2004

The first edition was Corrosion of Ceramics (Dekker, 1994).

Although great care has been taken to provide accurate and current information, neither the author(s) nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage, or liability directly or indirectly caused or alleged to be caused by this book The material contained herein is not intended to provide specific advice or recommendations for any specific situation Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe.

Library of Congress Cataloging-in-Publication Data

A catalog record for this book is available from the Library of Congress.

ISBN: 0-8247-5366-6

Headquarters

Marcel Dekker, Inc., 270 Madison Avenue, New York, NY 10016, U.S.A tel: 212–696–9000; fax: 212–685–4540

Distribution and Customer Service

Marcel Dekker, Inc., Cimarron Road, Monticello, New York 12701, U.S.A tel: 800–228–1160; fax: 845–796–1772

Eastern Hemisphere Distribution

Marcel Dekker AG, Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41–61–260–6300; fax: 41–61–260–6333

World Wide Web

The publisher offers discounts on this book when ordered in bulk quantities For more information, write to Special Sales/Professional Marketing at the head-quarters address above.

Copyright © 2004 by Marcel Dekker, Inc All Rights Reserved.

Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission

in writing from the publisher.

Current printing (last digit):

10 9 8 7 6 5 4 3 2 1

http://www.dekker.com

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my fatherHarry Sylvester McCauley1909–1966

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Preface to the Second Edition

Although a better understanding of the mechanisms of corrosion has occurred over the past ten years since the publication of the first edition

of this book, corrosion still remains a major problem One area in which some advances have been made is the understanding of the weathering mechanisms of building materials, especially where related

to monuments of the past The weathering of building materials has (Corrosion of Specific Crystalline Materials) Although the work on weathering of building materials has been done predominantly by civil engineers, it should be of interest to the ceramic engineer More information has become available concerning the corrosion of composite materials of all types The strong interest in composites materials has been enhanced by the aerospace industry and the military composite materials In addition, new sections have been added on all chapters where appropriate.

v

been added as new sections in Chapters 2 (Fundamentals) and 5

Because of this, a whole new chapter ( Chapter 7 ) has been devoted to bioceramics ( Chapter 5 ) New literature sources have been added to

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The first edition of this book was written to be used primarily as a reference book Questions have been added at the end of the most chapters and additional examples have been included along with recommended reading lists so that this second edition may also be used as a textbook for either a senior level undergraduate or a graduate course on corrosion.

Ronald A.McCauley

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Preface to the First Edition

One of the most important problems confronting engineers today is the development of materials that are reliable under various environmental conditions In some cases these conditions are considered extremely hostile—very high temperatures, mechanical loading, and/or aggressive chemical attack Ambient temperature aqueous attack can also be extremely detrimental, especially over an extended period of time, as in the case of hazardous waste disposal Engineers and scientists have been combating the attack upon ceramics

of molten glass, molten metals and slags, and molten salts for hundreds

of years with many improvements Most of these improvements have occurred through experimentation, eventually finding the material that worked best Only during the past 25 years has a true understanding of the complexities of corrosion of ceramics begun to develop Major advances have been made in recent years; however, the details in many cases are still questionable or at least debatable The cost to industry due to corrosion is considerable and only a thorough understanding of all the complexities of the process will help

vii

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to minimize that cost There will undoubtedly be many applications of ceramics where the ceramic will be consumed during service, but maximizing service life will greatly reduce the overall cost.

While several books, mostly in the form of symposia proceedings, have been published on various aspects of corrosion of crystalline and glassy ceramics, generally on the newer, advanced materials, none has addressed the subject in a comprehensive manner The most significant works have been reported in the technical literature; however, reading all the published articles is a formidable task This book is an attempt to discuss all aspects of the corrosion of ceramics, but no attempt has been made to complete an exhaustive literature review Although not all areas have been described in great detail, a summary of some of the most important work has been given with references for the interested reader This book is based upon a combination of lecture notes from the Advanced Refractories course that the author has taught at Rutgers during the past 15 years and the author’s industrial and consulting experiences It is intended predominantly as a reference work for practicing engineers and research scientists but could also be used as a text for a graduate-level course in corrosion of ceramics Any comments

or suggestions about the content of this book will be most welcome.

ACKNOWLEDGEMENTS

The author would like to thank the faculty and students of the Department of Ceramic and Materials Engineering at Rutgers, The State University of New Jersey, for many helpful and thoughtful discussions during the preparation of this book and especially Drs John Wachtman and M John Matthewson for reviewing a portion of the manuscript and for their valuable suggestions.

The author would like to extend a very special thank you to Mr William Englert of PPG Industries, who first introduced the author to the fascinating field of corrosion of ceramics.

Gratitude must also be extended to Mrs Mary Guerin for her help

in preparation of the manuscript and to Paul Mort, Robert Sabia, John Martin, and Ryan McCuiston for their help in preparing the figures The author would like to extend a very special thank you to his wife, Eleanora, and his son, Matthew, for their understanding during the many long hours required to complete this task.

Ronald A.McCauley

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Contents

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2.10 Summary of Important Concepts 105

2.12 Exercises, Questions, and Problems 108

3.8 Exercises, Questions, and Problems 140

4.5 Exercises, Questions, and Problems 164

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5 CORROSION OF SPECIFIC CRYSTALLINE

5.1.2 Attack by Aqueous Solutions 177

5.5 Exercises, Questions, and Problems 238

6.9 Exercises, Questions, and Problems 281

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7.2.1 Fibers 295 7.2.2 Fiber Coatings or Interphases 298

7.3.2 Nonoxide—Matrix Composites 309

7.7 Exercises, Questions, and Problems 321

8.5 Exercises, Questions, and Problems 364

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Introduction

If we begin with certainties, we shall end in doubt; but if

we begin with doubt, and are patient in them, we shallend in certainties

BACONMost engineers at one time or another will be confronted withcorrosion whether it will be their sole endeavor or whether itwill be a minor unexpected nuisance The actual study ofcorrosion, its causes, effects, and means of elimination is not

as common in the field of ceramics as it is in the field ofmetallurgy Although many engineers study the corrosion ofceramics all their lives, they normally do not considerthemselves as corrosion engineers, but as ceramic engineers orprocess engineers or possibly some other type of engineer Thereare no corrosion engineering courses offered in the several

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Throughout the history of the ceramic industries, variousmaterial types or compositions have been used because of someparticular advantageous, intrinsic property High strength, lowelectrical conductivity, or some other property may be theprimary concern for a particular application However,excellent resistance to attack by the environment always plays

a role and may, in some cases, be the prime reason for theselection of a particular material This is especially true forthose materials selected for furnace construction in the metaland glass industries

Almost all environments are corrosive to some extent Forpractical applications, it comes down to a matter of kinetics—how long will a material last in a particular environment? Insome cases, corrosion may be beneficial, such as in thepreparation of samples by etching for microscopic evaluation,

in chemical polishing to obtain a flat, smooth surface, or inbioactive materials where reaction with bone or completedisappearance is required The selective leaching of the sodium-and boron-rich phase in phase-separated borosilicate glass toproduce a high silica content glass (called Vycor™ *) is anexcellent example of how corrosion can be put to a beneficialuse Other examples include dissolution and reprecipitation in

* Corning, Inc., Corning, New York.

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Introduction 3

liquid phase sintering (also crystal growth studies) and thedissolution of various raw materials in molten glass in themanufacture of glass products

The proper selection of materials and good design practicescan greatly reduce the cost caused by corrosion To make theproper selection, engineers must be knowledgeable in the fields

of thermodynamics, physical chemistry, electrochemistry, andeven meteorology In addition, engineers must be familiar withthe corrosion testing of materials, the nature of corrosiveenvironments, the manufacture and availability of materials,and have a good sense of the economics of the whole process.There is a growing need in many ceramic applications to beable to predict the service life based upon laboratory tests.The limiting factors in making such predictions are more oftenthan not due to a lack of a thorough knowledge of the industrialoperating conditions rather than to devising the properlaboratory test A thorough knowledge of the microstructureand phase assemblage of the material, however, is critical to

an understanding of the corrosion that may take place TheNational Science Foundation has provided funding to severaluniversities* to develop a Digital Library of CeramicMicrostructures (DLCM), which, when completed, will be atremendous aid to the engineer involved in corrosion studies.This library will contain, in addition to selected micrographs,chemistry, phases, and some properties Access to the databasewill be via the Internet Although a material may be listed insome handbook as having excellent resistance to someparticular environment, it is important to know the form ofthe material Were the data listed for a single-crystal, a powder,

or a dense (or porous) sintered component? Were there any

* University of Dayton Research Institute has the primary role Georgia Institute

of Technology, North Carolina A&T State University, University of Rolla, along with Mechanical Test Instrumentation & Control are supplying the information.

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is the cost of the refractories involved, but also the cost of thetear out, the cost of the reconstruction, and the cost of anylost production is involved The total cost of such a repair canamount to as much as $10 million or more for a single furnace.Fig 1.1 shows an average estimate of the percentages for laborand materials for a typical furnace repair Business interruptioncosts have not been included since these will vary considerablydepending upon the product being produced and the size ofthe furnace The downtime for repairs also varies considerablydepending upon the extent of the repair, but varies between 1and 3 months The cost due to business interruption canamount to as much as $1 million per month There are,however, a few things that add a credit to the costs of a repair,

FIGURE 1.1 Glass furnace repair estimated cost percentages.

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Introduction 5

such as the fuel and raw materials saved during the shutdown.Thus it should be obvious that the equation to determine theexact costs of a particular repair is quite complex The totalcost of such repairs can never be eliminated; however, it can

be greatly reduced by the proper selection of refractories andthe proper operation of the furnace There are times when thecorrosion of the refractories goes unnoticed and failure occursprematurely Since furnaces are insured against prematurefailure, very large insurance claims have been filed In addition

to the costs related to the refractories, construction, and lostproduction are the costs related to additional cleanup due tothe failure and the costs of insurance adjusters and lawyers.The cost of such a failure can exceed $20 million

Environmental problems can also add to the total cost ofcorrosion For example, a trend toward the use of nonchrome-containing refractories for furnace construction has beenongoing for about the past 20 years Used refractories have, inthe past, been disposed of by burying them in landfills Chrome-containing refractories have the potential of contaminatinggroundwaters with hexavalent chrome, a carcinogen Ifchrome-containing refractories are used, upon disposal, theymust be hauled to toxic waste dumps with an added cost ofdisposal To eliminate this problem, some industries have beenleaning toward the use of other materials for the construction

of their furnaces In some cases, the replacement material doesnot last as long as the chrome-containing material, thusshortening the time between repairs and adding to the cost.The products of corrosion may enter the product beingmanufactured and lower the quality of the product or decreasethe yields Although this is a cost due to corrosion, it is onethat is extremely difficult to quantify Although no accuratenumbers are available for the annual cost to industry for thecorrosion of ceramic materials, an estimate of $2 billion doesnot seem unreasonable Only through the intelligent selection

of ceramic materials can the cost of corrosion be minimized.This intelligent selection of materials can be obtained onlythrough a thorough understanding of all the complexities of

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