Table Of Content'.
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3 8042 00117 0073
Techniques in Electrochemistry,
Corrosion and Metal Finishing
A Handbook
I
Techniques in Electrochemistry,
Corrosion and Metal
Finishing-A Handbook
Edited by
ANSELM T. KUHN
Harrow College of
Higher Education
with contributions by
M. Hayes, G. H. Kelsall, R. D. Rawlings, M. Spicer,
P. C. S. Hayfield, J. A. Kostuch and P. Neufeld
JOHN WILEY & SONS
hichester . New York· Brisbane' Toronto' Singapore
Dedication
At a time when research funds are scarcer than ever, the importance of well
funded Libraries is paramount. If we cannot do the work ourselves, at least~
/ through the Library~we can be informed of the findings of others. Let us
?;C>\l4-
therefore place our faith in those responsible for funding our major Libraries
SUP
that they appreciate the vital role that these play in the furtherance of research.
~ s:~
0 . Q.>c,,,,, k l! H The Library lies at the centre of all research, it is the seedcorn for the future.
Nor is it an organization whose funding level can be turned up and down from
CON
year to year since it represents a continuum of accessible information.
Even the best funded Library is only as good as its staff and in this, the
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Editor owes his deepest thanks to all those who have for so long been so
helpful, but especially to Mrs Vicky Tattle of the British Library (Science
Reference Division) whose knowledge is matched only by her unflagging
Copyright © 1987 by Joh~, Wiley & Sons Ltd. helpfulness and patience. Equally, John Kennedy, Librarian of the Royal
Society of Chemistry and his staff, have uncomplainingly assisted in the
All righ ts reserved. ,/"
checking of some of the thousands of reference.
\
", No part of this boo)s.~ay be reproduced by any means, or Last but not least, to Sylvia for all she has done and all she has had to put up
tra!1smitted, or translated into a machine language without the with~ Thank you! Perhaps we'll manage the next book with less mess!
writlefl 'permission of the publisher
Library of Congress Cataloging-in-Publication Data: A. T. K
Techniques in electrochemistry, corrosion, and
metal finishing- A handbook
Includes index.
I. Electrochemistry, Industrial. 1. Kuhn, Anselm.
H. Hayes, M.
TP255.M63 1987 660.2'97 86-26769
ISBN 0 471 91407 X
British Library Cataloguing in Publication Data:
Techniques in electrochemistry,
corrosion and metal finishing- A handbook
I. Electrochemistry- Laboratory manuals
1. Kuhn, Anselm 11. Hayes, M.
5413'7'028 QD557
Typeset by Bath Typesetting Lld, Bath
Printed in Great Britain by St "drnundsbury Press,
uffolk.
v
Contents
Contents
VU
List of contributors
IX
Introduction
XI
Part A: Introduction to experimental methods
1. Cell design- M. Hayes 3
2. Electrode design- M. Hayes 15
3. Instrumentation- M. Hayes 31
4. Ohmic drop-M. Hayes 43
5. Electrochemical techniques- A. T. Kuhn 55
6. The open-circuit potential decay (OCPD)
technique- G. H. Kelsall 75
7. The surface area and roughness
of electrodes-A. T. Kuhn 95
8. The purity and cleanliness of
solutions and electrodes- A. T. Kuhn 117
Part B: Specialized techniques
Section I: Methods based on the use of light, excluding spectroscopic
methods
9. Classification of methods and simple deductions from
visual observations-A. T. Kuhn and 1. A. Kostuch 143
10. Optical (non-spectroscopic) methods in corrosion and
electrochemistry- A. T. Kuhn 149
11. White-light reflectance methods- A. T. Kuhn 165
12. Methods based on the reflectance of monochromatic light:
electroreflectance, specular reflectance and other
techniques- A. T. Kuhn 171
13. Ellipsometry and its application to corrosion and
electrochemistry- P. C. S. Hayfield and A. T. Kuhn 187
ection II: Spectroscopic Methods
14. Introduction to spectroelectrochemistry- A. T. Kuhn 197
15. Infrared spectroelectrochemistry- l. A. Kostuch and
A. T. Kuhn 203
16. Transmission spectroelectrochemistry in the ultraviolet-
visible region and emission spectroscopy- A. T. Kuhn 219
17. Raman spectroscopy- A. T. Kuhn 237
18. Optically transparent electrodes- A. T. Kuhn 251
VII
viii Contents
Section Ill: Other Methods
19. Physicochemical methods for the determination of gaseous,
liquid and solid products formed in electrochemical and
List of Contributors
corrosion reactions- A. T. Kuhn 263
20. Thermometric and calorimetric methods in electrochemical
and corrosion studies- A. T. Kuhn 291 M. HA YES, GEC Hirst Laboratories, East Lane, Wembley, Middlesex
21. The application of radiochemical and isotopic methods to
HA97PP
corrosion and electrochemistry- A. T. K uhn 315
22. Acoustic emission methods- R. D. Rawlings 351 P. C. S. HAYFIELD, Research Dept. IMI p.\.c., Kynoch Works, Witton,
23. Electrical resistance measurement as a technique to follow Birmingham, B6 7DA
adsorption, corrosion or oxidation- A. T. Kuhn 409 G. H. KELSALL, Royal School of Mines, Imperial College, Prince Consort
24. Analysis of surfaces and thin films- M. Hayes 433
Road, London SW7 2BP
25. The use of dyes, markers, indicators and 'printing'
methods in corrosion and electrochemistry- A. T. Kuhn 465 .I. A. KOSTUCH, Royal School of Mines, Imperial College, Prince Consort
Road, London SW7 2BP
26. Experimental techniques for the study of anodic oxide
films- P. Neufeld and A. T. Kuhn 477 A. T. KUHN, Faculty of Science and Technology, Harrow College of Higher
27. Miscellaneous experimental techniques that have been Education, Northwick Park, Harrow HA I 3TP
applied to the study of electrochemical and corrosion
processes- A. T. Kuhn 491 P. NEUFELD, Dept. of Chemical Engineering, Polytechnic of the South Bank,
London, SE I OAA
Part C: The literature of electrochemistry and metal finishing corrosion R. D. RA WLINGS, Department of Metallurgy and Materials Science, Royal
28. The literature of electrochemistry and corrosion School of Mines, Imperial College, Prince Consort Road, London SW7
M. 1. Spicer 521 2BP
Index 561 M. 1. SPICER, British Library, Science Reference and Information Service, 25
Southampton Buildings, Chancery Lane, London, WC2A lAW
Road, London SW7 2BP
A. T. KUHN, Faculty of Science and Technology, Harrow College of Higher
Education, Northwick Park, Harrow HA I 3TP
P. NEUFELD, Dept. of Chemical Engineering, Polytechnic of the South Bank,
London, SE I OAA
R. D. RA WLINGS, Department of Metallurgy and Materials Science, Royal
School of Mines, Imperial College, Prince Consort Road, London
SW72BP
M. 1. SPTCER, British Library, Science Reference and Information Service,
25 Southampton Buildings, Chancery Lane, London, WC2A lAW
IX
Introduction
ABOUT THIS BOOK
This book has been written as a tool to be taken by the research worker wishing
to carve the shortest path to completion of the project in hand. By and large, we
have left it to others to expatiate on the various theories underlying the
techniques described. Those who wish to delve more deeply into the theoretical
aspects of particular methods will have no difficulty in locating suitable
reading, either from references in the individual chapters, or from chapter 28
'The literature of electrochemistry and corrosion'. Those whose need is more
I for practical details will also, we hope, find what they need, either described
directly or referenced.
What, then, are the aims of this book? Part A is addressed largely to those
with very little experience of practical work in electrochemistry or corrosion. It
sets out certain basic tenets and considers the 'hardware' that is needed for
almost all types of work. Also considered are the broad questions of purity and
cleanliness, as well as the measurement of surface area and roughness. These
are questions that should concern almost all workers in the field. Part A
concludes with a description of some of the simplest electrochemical techniques
and some of the practical details and dangers involved for those who might
wish to use them.
Part B is of a somewhat different character. Here, a series of specialist
techniques are considered in some depth, and it is quite probable that, in the
light of their particular needs, readers will focus on particular chapters rather
than reading through from cover to cover. Out of all this it is the hope of the
authors that there will be very few practitioners who will not find something
interesting or useful in what has been collected here.
Part A, then, is directed largely at the novice, while Part B is aimed both at
the worker with an eye on a specific technique as well as at the researcher who,
knowing the nature of the problem to be tackled, has yet to decide on the
appropriate means of so doing. The first of these will find in each case as full a
bibliography as possible describing the various means of implementing the
technique in question and also the systems to which it has been applied. For the
worker who has yet to decide what method to use, by reference to the examples
of systems that have been studied using each technique, we hope that it will be
asy to ascertain whether a given method is potentially useful. Lastly, for the
'techniques man' casting around for new ideas, we hope some of the more
c' teric methods described will be of interest, whether as a foundation on
which to build, or more prosaically, to avoid a reinvention of the wheel.
XI
xii Introduction Introduction xiii
In writing a book on techniques, does one simply describe them and leave the and catalogues. All this is tedious. But the greatest demand of all, and one at
choice open, or does one endeavour to steer the reader in certain directions? which so many baulk, is the sheer mental effort of reading a considerable
Without answering this question, the following observation is made. Aca number of papers, assimilating them and distilling from the whole a reasoned
demics are a long-lived breed, and coupled with this is the pressure upon them summary of the situation as the literature shows it. Only those who have
to publish. All too often one sees academics who have run out of ideas, and it is completed this 'trial by ordeal' are truly entitled to proceed to the next stage.
largely from these that the proliferation of 'techniques papers' emerge. Increas Some researchers are seemingly incapable of this distillation process, and can
ingly such new techniques are dignified with acronyms. Older and longer only produce a chronology of the subject- a much less useful exercise.
established acronyms, like SEM (for scanning electron microscopy), are univer Admittedly there is little more daunting than that initial session in the library,
sally recognized conveniences. Newer ones, one suspects, are an attempt by where one begins, knowing perhaps very little of the subject in question, and
their perpetrators to confer a greater importance on a given technique than where one recognizes that the goal is to emerge fully conversant with the
perhaps it deserves, in an attempt to 'validate' it. Readers can decide for current situation in the field. The best way to make such a search is by means of
themselves who is playing this particular game! Chemical Abstracts. This is partly because they are among the best organized
In contrast to the academic, who may spend a lifetime in pursuit of the finer and indexed and also because they cover, at their periphery, most of the other
nuances of, for example, electrochemical ESR (electron spin resonance), the topics likely to be of interest to readers of this book. There must be very few
industrial researcher tends to be flung from one discipline to another. Coming significant publications in electrochemistry or corrosion that are not indexed by
fresh to electrochemistry, the first (and by no means mistaken) instinct will be Chemical Abstracts. Nevertheless, there are other abstracting journals and there
for such scientists to attend a conference on the subject. The danger of so doing may be occasions when it is felt wise to use these. The widespread availability of
is that they will not realize that the speakers have a vested interest, in 'puffing' computer-based literature searching can reduce time spent poring through
their latest techniques, totally different from that of the industrial scientist, indexes, though most such databases do not reach back beyond 1967 or 1970.
concerned only to find the shortest path to a solution of his problem. This book Experienced library users express a healthy scepticism of computer searches
seeks to be a corrective influence against such effects. and, where the worker already has some pertinent references, which is usually
The purpose of this book, then, is to be the 'first port of call' for newcomers. the case, it is useful to see if the computer search locates all of these. If not, then
In no way do we claim to offer the last word. That role is gladly ceded to it should be clear that either somewhat inappropriate keywords have been used
anyone willing to accept it. or some more fundamental weakness of the system has been revealed. There is
still much to be said for the manual search, not least because serendipity so
often occurs in this way.
USE OF THE LITERATURE Completion of a rigorous literature search is a time-consuming task, and one
that most scientists prefer to avoid. Since most aspects of corrosion and
Research is a chore, a duty, a challenge, a habit, a way of life, an intoxicating
electrochemistry have, at one time or other, formed the subject of a monograph
drug. Less emotiveiy, perhaps, one may describe it as a sequence of processes.
or review, we saw the inclusion of the chapter on The literature of electrochem
Initially, there is the identification of the problem, or the recognition of a need
istry and corrosion' as a key element in getting newcomers to a field speedily
for specific data or information. Or perhaps there will be a call for experimental
focused on a relevant body of literature. Though the relevance of work cited in
verification of a hitherto abstract idea. Following this stage, an experimental
that chapter cannot inevitably be 100 per cent, we feel confident that it will be
programme must be formulated, but not until the questions posed have been
invaluable for speedy 'homing-in'.
set into the context of existing knowledge.
At the culmination of any research programme, it is customary to assess the
The editor recognizes that the importance laid by him on a thorough search
value of the results obtained. Are they sufficiently novel to be worth publi
of the literature before embarking on practical research exceeds that of most of
cation? Are they patentable in terms of prior published art? These questions
his colleagues. In this, he is wholly unrepentant. Too many times has one seen
can only be resolved in the library. Far better to have the information before
research completed, only for those involved to learn that they were long ago
starting out on a project than to learn the truth at its conclusion. In this book
pre-empted in their tasks. So many times has one seen errors repeated,
we offer ideas and choices; we do not seek to make rules or prescriptions. But if
published warnings unheeded. Literature searching is, to the great majority of
there is to be an exception to this liberality, then that would be the insistence
scientists, an unwelcome task. Tt involves a journey from the comforts of the
that the literature must not just be located, but actually read. One has
office or laboratory to the library. It involves a searching of indexes, shelves
encountered publication which ugge t trongly that, after completion of
xiv Introduction Introduction xv
in many research establishments in East and West, in the Developed and
research, the authors carried out a literature search (probably using a com
Developing Worlds. Everywhere, one sees laboratories where the personnel
puter) and simply appended this to the completed paper.
have remained virtually unchanged for the past 5- 10 years. The resulting
It is not really for the writer to instruct readers how to study the literature.
stagnation has meant a loss of vitality and activity.
Published information is of a partly qualitative, partly quantitative nature, and
Too many laboratories have more than their fair share of workers who have
it is in respect of the latter that a word of advice will be offered. Wherever
lost their way, run out of inspiration, been defeated by their own poor research
possible, in reading a number of papers on a given subject, one should seek to
strategy or have found themselves unable to complete their work by writing it
extract numerical data, and tabulate it or plot it graphically. Only in this
up. Lack of self-discipline, inability to organize themselves, chronic mild
fashion do anomalies emerge, which can give clues of various kinds. Looking
depression are phenomena all too often encountered. Then there are those who,
for an example to illustrate this, the author recalls his (unpublished) survey of
one suspects, lack the confidence to share their findings with the scientific
open-circuit potential-time data on Co-Cr alloys. Each paper presented
community and others, still, so sublimely confident of their ability, who seem
seemingly reasonable data. Applying simple theory, semi logarithmic plots
not to feel the need to do so.
could be obtained in each case. What did emerge, however, was that very few of
In the future those who are charged with the management of research will
these had the same gradient, and, as a result, the attractive simplicity of the
come under growing pressure to be aware of the human factors operating in a
proposed theory collapsed, and it became apparent that hitherto unregarded
research environment to the extent that their task will become much more than
factors were, in effect, important parameters.
the administration of budgets and the formulation of overall policies. Rather,
A second goal in assimilation of published data should be to wrest the
they will need to be aware of the dynamics of the research process, they will
absolute maximum of information from each publication. It is surprising how
need to recognize the sort of foibles described here and gently but firmly
often authors have published data, yet failed to apply appropriate theoretical
counteract them.
treatment. Using a computer and digitizing tablet, published data in graphical
form can be reconverted to numerical data prior to application of some other
theoretical approach. Alternatively, current-voltage plots can be retrospec Planning the research
tively corrected for ohmic error. No literature search is complete until all these
Good planning in research, as in so many other activities, is the key to a
approaches have been explored, and perhaps, too, a listing of parametric effects
successful outcome of the exercise and as such it is a wholly laudable activity.
has been made, where the effects (as noted by various authors) of change of
To a large extent, the formulation of a plan prejudges the outcome of the work,
potential, pH, temperature, reactant concentrations, are summarized. There is
and one of the most difficult decisions to be taken by an experimentalist is
no clearer and more dramatic means of identifying discords or lacunae in the
whether, should an unexpected twist occur, this should be followed up or left as
literature.
an unexplored alley. The research plan will be based on an analysis including
questions such as:
RESEARCH AND RESEARCHERS- THE HUMAN ELEMENT
(a) What is the (real) problem?
Whatever the technique, it can be no better than the scientist who chooses it, (b) What do we need to know or find out?
operates it and produces research using it. Physical scientists are not known for (c) What is the present sum of our knowledge?
the acuity of their observations on their fellow men, and yet they are not short (d) What human/financial/equipment resources are available?
of quirks and eccentricities, many of which stand between them and the
A search of the literature and consultation with known experts allows a flying
achievements of which they are capable. Many will recognize the species
sta rt in respect of the third of the questions above and will also be invaluable in
'equipment hoarder' and the related 'equipment constructor' for whom the
answering the first two. The fourth question relates to the number of people
building of apparatus eclipses in importance the task for which it was designed.
available for tackling a problem, their levels of expertise and the time for which
Researchers are notoriously slow to seek advice from their peers, or from
lhey are available. It is to be hoped that the equipment requirements will not
experts in related fields, and this is as true of industrial as academic workers.
necessarily be restricted to those 'in house' but will take into account the
Today, however, research budgets in most laboratories around the world are
willingness with which many organizations allow their equipment to be used by
under pressure, and collaboration and sharing make better sense than ever
lhers, whether this be gratis or on payment of a fee.
before. Even more relevant are the workings of demography and the economy.
It is suggested here that most research projects (or at least components of
The e twin factors have conspired to create something approaching a standstill
