Marcus P. Corrosion mechanisms in theory and practice

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Corrosion Mechanisms

in Theory and Practice

Second Edition, Revised and Expanded

edited by

Philippe Marcus

Laboratoire de Physico-Chimie des Surfaces

Université Pierre et Marie Curie

Ecole Nationale Supérieure de Chimie de Paris

Paris, France

ARCEL DEKKER, INC.NEW YORK • BASEL

First edition published as Corrosion Mechanisms in Theory and Practice edited by

P. Marcus and J. Oudar.

ISBN: 0-8247-0666-8

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Preface

Corrosion is a major issue for the increase of service life and reliability of metallic

materials. A detailed understanding of the mechanisms of corrosion helps us to solve

existing corrosion problems and to prevent future problems.

The aim of this book is to review recent advances in the understanding of

corrosion and protection mechanisms. A detailed view is provided of the chemical

and electrochemical surface reactions that govern corrosion, and of the link between

microscopic forces and macroscopic behavior, is provided.

In order to cover fundamental as well as practical aspects, the second edition,

which has been revised and expanded (three new chapters have been added) contains

in 19 chapters. Chapters 1 to 13 cover the basic phenomena in corrosion: adsorption,

entry of hydrogen, anodic dissolution, passivation, passivity breakdown and

localized corrosion (pitting and crevice corrosion), stress corrosion cracking, and

corrosion fatigue. Chapters 14 to 19 provide the connection between the theoretical

aspects of corrosion mechanisms and practical applications in industry: corrosion

inhibition, atmospheric corrosion, microbially induced corrosion, corrosion in

nuclear systems, corrosion of microelectronic and magnetic data-storage devices,

and the technologically important area of corrosion protection by surface coatings.

This book is based on the results of intensive worldwide research efforts in

materials science, surface science, and corrosion science over the past few years. The

contributors, from leading academic and industrial research institutes, are highly

recognized scientists in these disciplines.

Philippe Marcus

iii

Contents

Preface iii

Contributors vii

BASIC PHENOMENA

1. Introduction to Surface Reactions: Electrochemical Basis

of Corrosion 1

Dieter Landolt

2. Introduction to Surface Reactions: Adsorption from

Gas Phase 19

Jacques Oudar

3. Surface Effects on Hydrogen Entry into Metals 53

Elie Protopopoff and Philippe Marcus

4. Anodic Dissolution 97

Michel Keddam

5. Thin Oxide Film Formation on Metals 171

Francis P. Fehlner and Michael J. Graham

6. Growth and Stability of Passive Films 189

Barry MacDougall and Michael J. Graham

7. Passivity of Austenitic Stainless Steels 217

Clive R. Clayton and Ingemar Olefjord

8. Mechanisms of Pitting Corrosion 243

Hans-Henning Strehblow

9. Sulfur-Assisted Corrosion Mechanisms and the Role

of Alloyed Elements 287

Philippe Marcus

10. Further Insights on the Pitting Corrosion of Stainless Steels 311

Bernard Baroux

11. Crevice Corrosion of Metallic Materials 349

Pierre Combrade

12. Stress-Corrosion Cracking Mechanisms 399

Roger C. Newman

13. Corrosion Fatigue Mechanisms in Metallic Materials 451

T. Magnin

APPLICATIONS

14. Corrosion Prevention by Adsorbed Organic Monolayers

and Ultrathin Plasma Polymer Films 479

Michael Rohwerder, Guido Grundmeier, and Martin Stratmann

15. Atmospheric Corrosion 529

Christofer Leygraf

16. Microbially Influenced Corrosion 563

Dominique Thierry and Wolfgang Sand

17. Corrossion in Nuclear Systems: Environmentally Assisted

Cracking in Light Water Reactors 605

F. P. Ford and Peter L. Andresen

18. Corrosion of Microelectronic and Magnetic Data-Storage Devices 643

Gerald S. Frankel and Jeffrey W. Braithwaite

19. Organic Coatings 683

J. H. W. de Wit, D. H. der Weijde, and G. Ferrari

Index 731

vi Contents

Contributors

Peter L. Andresen Corrosion Coatings and Joining Research and Development

Center, General Electric Company, Schenectady, New York

Bernard Baroux Ugine Research Center, Ugine-Savoie, Ugine, France

Jeffrey W. Braithwaite Sandia National Laboratories, Albuquerque, New Mexico

Clive R. Clayton Department of Materials Science and Engineering, State

University of New York at Stony Brook, Stony Brook, New York

Pierre Combrade FRAMATOME, Centre Technique, Le Creusot, France

J. H. W. de Wit Netherlands Institute for Metals Science, Delft University of

Technology, Delft, and Corus Research and Development, Ijmuiden, The

Netherlands

Francis P. Fehlner Department of Advanced Materials, Corning Incorporated,

Corning, New York

G. Ferrari TNO Industrie, Den Helder, The Netherlands

F. P. Ford Corrosion Coatings and Joining Research and Development Center,

General Electric Company, Schenectady, New York

Gerald S. Frankel Department of Materials Science and Engineering, Fontana

Corrosion Center, The Ohio State University, Columbus, Ohio

Michael J. Graham Institute for Microstructural Science, National Research

Council of Canada, Ottawa, Ontario, Canada

vii

Guido Grundmeier Department for Interface Chemistry and Surface Technology,

Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Michel Keddam Laboratoire de Physique des Liquides et Electrochimie,

Université Pierre et Marie Curie, Paris, France

Dieter Landolt Département des Matériaux, Laboratoire de Métallurgie

Chimique, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Christofer Leygraf Division of Corrosion Science, Department of Materials

Science and Engineering, Royal Institute of Technology, Stockholm, Sweden

Barry MacDougall Institute for Environmental Chemistry, National Research

Council of Canada, Ottawa, Ontario, Canada

T. Magnin Ecole Nationale Supérieure des Mines de Saint-Etienne, Saint-Etienne,

France

Philippe Marcus Laboratoire de Physico-Chimie des Surfaces, Université Pierre

et Marie Curie, Ecole Nationale Supérieure de Chimie de Paris, Paris, France

Roger C. Newman Corrosion Protection Center, University of Manchester

Institute of Science and Technology, Manchester, England

Ingemar Olefjord Department of Engineering Metals, Chalmers University of

Technology, Göteborg, Sweden

Jacques Oudar Laboratoire de Physico-Chimie des Surfaces, Université Pierre

et Marie Curie, Ecole Nationale Supérieure de Chimie de Paris, Paris, France

Elie Protopopoff Laboratoire de Physico-Chimie des Surfaces, Université Pierre

et Marie Curie, Ecole Nationale Supérieure de Chimie de Paris, Paris, France

Michael Rohwerder Department for Interface Chemistry and Surface Technology,

Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Wolfgang Sand Universität Hamburg, Hamburg, Germany

Hans-Henning Srehblow Institut für Physikalische Chemie und Elektrochemie,

Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany

Martin Stratmann Department for Interface Chemistry and Surface Technology,

Max-Planck-Institut für Eisenforschung GmbH, Dusseldorf, Germany

Dominique Thierry Swedish Corrosion Institute, Stockholm, Sweden

D. H. van der Weijde Corrus Research and Development, Ijmuiden, The

Netherlands

viii Contributors

Introduction to Surface Reactions:

Electrochemical Basis of Corrosion

Dieter Landolt

Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

INTRODUCTION

Most corrosion phenomena are of electrochemical nature. They imply two or

more electrode reactions: the oxidation of a metal (anodic partial reaction) and

the reduction of an oxidizing agent (cathodic partial reaction). To understand

corrosion reactions one needs to study electrochemical thermodynamics and

electrochemical kinetics of the partial reactions. For example, the corrosion of

zinc in an acid environment proceeds according to the overall reaction:

This reaction includes the anodic partial reaction (2) and the cathodic partial

reaction (3):

The corrosion rate depends on the electrode kinetics of both partial reactions. In

principle, it can be predicted if all electrochemical parameters of the anodic and

cathodic partial reactions are known. According to Faraday’s law, there is a linear

relationship between the metal dissolution rate at any potential,

, and the

partial anodic current density for metal dissolution i

a,M

In this equation n is the charge number (dimensionless), which indicates the number

of electrons exchanged in the dissolution reaction, and F is the Faraday constant,

F = 96,485 C/mol. In the absence of an external polarization a metal in contact with

an oxidizing electrolytic environment acquires spontaneously a certain potential,

called the corrosion potential, E

cor

. The partial anodic current density at the corrosion

potential is equal to the corrosion current density i

cor

. Equation (4) thus becomes:

The corrosion potential always lies between the equilibrium potentials of the

respective anodic and cathodic partial reactions. Its exact value is determined by

the kinetics of the partial reactions.

ELECTROCHEMICAL THERMODYNAMICS

Electrochemical thermodynamics predicts the equilibrium potential of the partial

reactions. The overall stoichiometry of any chemical reaction can be expressed by

Eq. (6).

2 Landolt

Here the symbol B

designates the reactants and products. The stoichiometric

coefficients v

of the products are positive and of the reactants negative. The free

enthalpy of reaction ΔG is

Here μ

is the chemical potential of the participating species. If reaction (6) is

carried out in an electrochemical cell, the corresponding equilibrium potential E

rev

is given by

By analogy, under standard conditions (all activities equal to one) one gets

where ΔG° represents the standard free enthalpy and E° represents the standard

potential of the reaction.

It is common to write electrode reactions in the general form

Here v

ox,i

represents the stoichiometric coefficient of the “oxidized” species, B

ox,i

appearing on the left side of the equality sign together with the free electrons, and

red,i

indicates the stoichiometric coefficients of the reduced species, B

red,i

, appearing

on the right side of the equality sign, opposite to the electrons. Equation (10)

corresponds to a partial reduction reaction and the stoichiometric coefficients

ox,i

and v

red,i

are both positive.

By setting the standard chemical potential of the solvated proton and of

molecular hydrogen equal to zero, μ°

= 0, μ°

= 0, one can define the standard

potential of the partial reduction reaction (10) with respect to the standard hydrogen

electrode. The standard potential of an electrode reaction thus corresponds to the

overall reaction:

Table 1 indicates the standard potential of selected electrode reactions. Extensive

compilations of data can be found in Refs. 1 and 2.

The chemical potential of a species B is defined by (12), where a

represents

its activity.

Electrochemical Basis of Corrosion 3

TABLE 1 Standard Potentials of Electrode

Reactions at 25°C

Introducing (12) into (7) applied to reaction (11), one obtains for the free enthalpy

of reaction

With (8) and using a

H+

= 1, P

= 1 bar for the standard hydrogen electrode, one

obtains the Nernst equation (14) of an electrode reaction. It expresses the variation

of the equilibrium potential E

rev

with respect to the standard hydrogen electrode

as a function of the activities of the participating species B

ox,i

and B

red,i

In Eq. (14) the activity of pure substances is equal to one. The activity of dissolved

ions cannot be determined unless nonthermodynamic assumptions are made. In

corrosion one usually replaces the ionic activities by the respective concentrations.

Thus for the electrode reaction (2) one obtains

Using the data of Table 1 and replacing the natural logarithm by the logarithm base

10, this yields for 25°C