Passivity and Protection of Metals Against Corrosion

217 Pages·1967·12.53 MB·English

by  Nikon D. Tomashov

Passivity and Protection
of Metals Against Corrosion
Passivity and Protection
of Metals Against Corrosion
Nikon D. Tomashov
and Galina P. Chernova
Institute of Physical Chemistry
Academy of Sciences of the USSR
Translated from Russian by
Boris H. Tytell
Consulting Engineer
Greenwood, Massachusetts
Translation Editor
Herbert H. Uhlig
Department of Metallurgy
Massachusetts Institute of Technology
Cambridge, Massachusetts
With a Foreword by
Edward C. Greco
Research Department
United Gas Corporation
Shreveport, Louisiana
~
PLENUM PRESS· NEW YORK· 1967
Nikon Danilovich Tomashov, Scientific Superintendent of the Alloy Corro
sion Laboratory of the Institute of Physical Chemistry of the Academy of
Sciences of the USSR, has been active for thirty years in research on cor
rosion and the protection of metals. His work on the theory of corrosion
processes and the principles of corrosion-resistant alloying and his de
velopment of new methods for the protection of metals have been given
wide recognition and have found important practical applications. Profes
sor Tomashov's fundamental work Corrosion Theory and the Protection of
Metals has been translated into English and published in the USA in 1966
by the Macmillan Company. In 1966, he was awarded the W. R. Whitney
medal by the American National Association of Corrosion Engineers.
Galina Prokof'evna Chernova, Senior Scientific Worker in the Corrosion
Department of the Institute of Physical Chemistry of the Academy of
Sciences of the USSR, completed her· studies at the Moscow Institute of
Steel and Alloys in 1947. Her research concerns fundamental work in the
field of the passivity of alloys.
The Russian text, originally published for the Institute of
Physical Chemistry, Academy of Sciences of the USSR, by
Nauka Press, Moscow, 1965, has been revised by the authors
for the American edition.
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PASSIVNOST'I ZASHCHITA METALLOV OT KORROZII
PASSIVITY AND PROTECTION OF METALS AGAINST CORROSION
Library Congress Catalog Card Number 66-19933
lSBN-13: e-lSBN-13: 978-1-4684-1728-9
978-1-4684-1730~2
DOl: 10.1007/978-1-4684-1728-9
© 1967 Plenum Press
Soficover reprint oft he hardcover 1st edition 1967
A Division of Plenum Publishing Corporation
227 West 17 Street, New York, N. Y. 10011
All rights reserved
No part of this publication may be reproduced in any
form without written permission from the publisher
Foreword
Considerable progress has been made in the past 20 years toward
understanding the basic mechanisms of corrosion, and the application
of this knowledge to its control. From the very beginning, educational
institutions and industrial research laboratories have contributed
greatly toward determining and elucidating the fundamental principles
of corrosion reactions. Some of the basic principles involved in cor
rosion of metals can be credited to early investigators. Michael
Faraday in 1830-1840 studied the relationship between the quantity of
a metal dissolved and the electric current which was produced by this
reaction. He also proposed that the passivation of iron was through
the formation of a film and that the dissolution of a metal was electro
chemical in nature. Sir Humphrey Davy in 1824 worked out the funda
mentals of galvanic corrosion of ships' hulls and applied sacrificial
zinc anodes to protect them from sea water corrosion. Richard Arlie
in 1847 demonstrated that corrosion produced by oxygen at the surface
of iron in a flowing stream generated a current. With the fundamental
knowledge available to him from these early investigators, Willis
Rodney Whitney developed and expressed, in its most useful form, one
of the basic scientific principles which provides modern corrosion
specialists with a fundamental basis of corrosion control. Dr. Whitney
concluded that corrosion of iron is electrochemical, and that the rate
is simply a function of the electromotive force and resistance of the
circuit.
It is indeed fitting that I had the privilege during the Third Inter
national Congress on Metallic Corrosion in Moscow, May 1966, of
presenting to the senior author of this volume, Professor Tomashov,
the NACE Willis Rodney Whitney Award, in recognition of his notable
and extensive contributions to the science of corrosion.
Scientists and engineers of many countries have contributed to the
rapid development of corrosion science, and prominent among these
v
vi FOREWORD
are the corrosion specialists of the Soviet Union. Professor Tomashov
and Galina P. Chernova are among the respected contributors and
leaders of corrosion research in the USSR. Their research has re
received world-wide acclaim. Professor Tomashovhas spent 35 years
in scientific research and is presently director of the laboratory of
alloy corrosion at the Institute of Physical Chemistry in Moscow. His
work on the theory of electrochemistry as applied to the investigation
of passivity of metals, electrochemical and corrosion behavior of
stainless and copper steels, titanium and its alloys, and new ways of
increasing the corrosion resistance of alloys by alloying them with
more noble elements, is well known and widely acclaimed. Professor
Tomashov is the author of 200 papers and 6 books on corrosion tech
nology.
Throughout this volume he and Galina Chernova have presented
the subject of passivity in a very clear and skillful manner. The book
includes 6 chapters: the phenomenon of passivity in metals, passive
systems, basic principles for increasing the corrosion resistance of
alloys by increasing their passivity, anodic protection, passivation of
metals by contact with cathodes, and passivation of metals by the
introduction of oxidizers into the corrosive medium.
In Chapter 4, the authors do a commendable job of discussing the
basic concepts and application of anodic protection, one of the more
recent methods employed for protection of metals against corrosion.
They cover in a concise manner the effectiveness of anodic protec
tion, the effect of various factors on the parameters of anodic protec
tion, including the radius of effective protection, anodic protection
against intergranular corrosion, the effect of anodic polarization on
corrosion cracking, the effect of halide ions, and the anodic protection
of carbon steels and titanium. Corrosion specialists and students will
find this excellent and informative volume indispensible; they are
indebted to Professor Tomashov and Galina Chernova for this fine
contribution to the literature on corrosion technology. They are also
indebted to Mr. Tytell for his painstaking and first-rate translation,
and to Professor Uhlig for his work of editing the translation.
I wish to add my thanks for the privilege of writing the Foreword
to Passivity and Protection of Metals Against Corrosion and extend
my gratitude to Professor Tomashov and Galina P. Chernova for
making this useful monograph available to corrosion students and
specialists in the English -speaking countries.
Shreveport, Louisiana Edward C. Greco
April 24, 1967
Preface
Various new methods for upgrading the corrosion resistance of
metals and alloys have become available within the past decade. Some
of the most interesting and important of these deal with the phenomenon
of passivity and with the so-called passive metals. This category of
metals encompasses, among others of the transition group, titanium,
chromium, zirconium, and nickel, plus their alloys including the stain
less steels. Major improvements in these metals have been paralleled
by the introduction of anodic protection using applied electric currents.
This has been established as an effective new technique for corrosion
control, particularly in the chemical industry.
Professor Tomashov and his associates occupy a primary role in
these world-wide developments. They have through their own re
searches advanced the forefront of corrosion science, and, at the same
time, have shown how these advances can be interpreted in terms of
practical alloys and corrosion inhibitors. The principles they care
fully present, many of which they developed themselves, are in accord
with advanced concepts of the electrochemical theory of passivation,
and are essential to an understanding of the remarkable alloys to which
these principles lead. The basic theory, in this connection, is also
necessary to an understanding of how the improved alloys are best
used in practice.
In addition, the book contains detailed practical data on the cor
rosion and electrochemistry of passive metals and alloys which have
not heretofore been made available in English. This feature plus a
complete description of underlying theory and practice insure that
the book will be welcomed by corrosion engineers, chemical engineers,
materials scientists, and by a broad segment of corrosion students who
wish to keep abreast of developments in a rapidly changing scientific
and engineering discipline.
Cambridge, Massachusetts H. H. Uhlig
May 8. 1967
vii
Preface to the American Edition
The authors of the book were gratified to learn that their work was
to be translated into English, and would thus become more accessible
to a wide circle of scientific and technical specialists in the United
States, where considerable attention is given to the study of the cor
rosion of metals-and particularly to means of combating it.
With the awareness both of the requirements and the pressing
questions of new technology, development of the science of the corro
sion and protection of metals has been given renewed impetus in
recent decades. In the past, the attention of scientists has been
directed mainly to research on the passivity of metals-and this is
understandable-since the passivity of metals is not merely an
interesting natural phenomenon, attracting the attention of inquiring
minds, but, at the same time, it is the principal cause of the relative
durability of the majority of industrial metals and alloys, which by
their nature are thermodynamically unstable.
Research on the mechanism of the passivity of metals and the
principal factors which determine their transition to the passive
state and, conversely, their activation, as well as on the development
of new methods of investigating passivity, is currently proceeding on
a wide front, and often along similar lines, in a number of industrially
developed countries.
In recent years, considerable attention has been devoted to the
development of methods of application of available scientific achieve
ments in the field of passivity toward a solution of the practical prob
lem of increasing the effectiveness of anticorrosion protection, and
to the development of new, more corrosion-resistant alloys.
In this connection, there has been definite progress not only in
improving already known methods of prqtection-for example, pro
duction of more effective anodic inhibitors, improvements in the
passivating surface treatment of metals, production of alloys for
ix
x PREF ACE TO AMERICAN EDITION
direct inhibition of the anodic process, and so forth-but also in the
discovery and practical application of fundamentally new methods of
protection, unknown 10 or 20 years ago, such as cathodic alloying of
alloys, application of anodic electrochemical protection, and others.
The discovery of these methods has not been an accident, but the
logical outcome of lengthy and systematic research in the study of
the kinetics of corrosion processes in passivating systems.
These methods, first proposed in the USSR, have been further
developed in the USA, where the maximum achievements are currently
being obtained in th.'eir practical application. Examples are the adop
tion in the USA of the industrial production of cathodically alloyed
metals (e.g., titanium base) and the application ofthe method of anodic
protection in industry. The practical experience acquired in the USA
in this field will undoubtedly be useful in the development of these new
methods of protection.
Since the translation of our book follows fairly soon after its first
publication in the USSR, there is as yet no need to undertake any
radical revision of the book for the American edition. Slight amend
ments and additions have been made by the authors at the request of
the American publisher.
The authors express their sincere gratitude to Professor H. H.
Uhlig, who has undertaken the task of the scientific editing of the
translation of our book, and to the American publisher for the careful
preparation of the translation.
N. D. Tomashov and G. P. Chernova
Preface to the Russian Edition
With the development of the science dealing with corrosion and
protection of metals, various anticorrosion approaches and methods
for preserving metallic structures are continually being refined and
improved. New methods which make it possible to use metals and
alloys under more and more complex technological conditions are
being developed. There can be no doubt that progress in the develop
ment of corrosion protection can be achieved only by the simultaneous,
thorough development of the scientific study of corrosion phenomena
and by the establishment of quantitative relationships between the
kinetics of corrosion processes and the various factors promoting
them, on the part of both the metal and the corrosive medium. The
technology of corrosion protection and the scientific methods for
investigating corrosion processes under a variety of conditions are
being studied intensively at present.
One of the basic problems of corrosion theory is, without doubt,
the problem of passivity. It presently attracts the attention of many
scientists. The authors of this book devoted many years to the
investigation of passivity. Studies were carried out to determine the
essence of the phenomenon and the mechanism involved in establishing
the passive state in metals and alloys, and to develop methods for
investigating this complex phenomenon of passivity for the purpose
of enhancement of corrosion resistance in practical metallic systems.
An attempt has been made to summarize briefly the results of our
past investigations as well as our most recently published data on im
proving the corrosion resistance of metals and alloys by increasing
their passivity and maintaining their stable passive state.
The results of investigations on these problems are scattered
throughout many journals, and they do not always include ways and
means of utilizing these phenomena for corrosion protection. Methods
for increasing the corrosion resistance of metals by increasing their
xi
xii PREF ACE TO RUSSIAN EDITION
passivity (alloying with cathodic elements, anodic protection, use of
cathodic couples) are, for the most part, accomplishments of Soviet
science. However, their utilization, unfortunately, lags behind
experimental applications abroad.
We hope that the systematic presentation in this work of problems
in the field of passivation and corrosion resistance will promote a
much wider application of the new methods and a more extensive use
of established methods of protection based on increased stability of
the passive state. We hope, too, that the present volume will be use
ful in the solution of specific problems on protection corrosion
arising with the expansion of the chemical industry.
A few words are in order concerning the content and arrange
ment of the book. In the Introduction, we discuss briefly the importance
of passivity as one of the methods available in the battle against metal
corrosion. In Chapters I and II, the modern theory of passivity, the
kinetics of passivation processes, and the methods used for investi
gating passivity and the structure of passive films are presented.
In Chapters III, IV, and V, we discuss the more original material
dealing with the basic principles involved in increasing the corrosion
resistance of alloys by increasing their passivity, the new principle
of anodic protection of metallic structures, and the use of cathodic
couples. The authors' investigations throughout many years on
problems of passivity in metals and alloys are summarized in these
sections. We also deemed it necessary to dwell briefly on some
insufficiently investigated aspects of anodic protection, such as the
introduction into the solution of metallic cations of electropositive
metals and the effect of electrochemical protection on cathodic
coatings.
Chapter VI is devoted to the practically important and scientifically
interesting problem of increasing corrosion resistance by introducing
passivators (oxidizing inhibitors) into the corrosive medium.
Problems on the protection of metals by processing in passivating
solutions or by anodic oxidation-that is, methods of protection
associated with the formation on the metal surface of protective
films resulting from· prior surface treatment-are not discussed in
this book, although they too present an opportunity to apply directly
the phenomenon of passivity to practical corrosion protection. These
methods have been widely used for some time and are fully described
in special books and articles on the subject.
The authors humbly invite any criticism and comments by the
readers of this volume.
N.D. Tomashov and G. P. Chernova