Nickel and chromium plating

463 Pages·1993·38.924 MB·English

by  J. K. Dennis

Nickel and chromium plating

J.K. DENNIS and T.E. SUCH
Nickel and
chromium plating
THIRD EDITION
W O O D H E A D P U B L I S H I N G L I M I T E D
CAMBRIDGE ENGLAND
Published by Woodhead Publishing Ltd
Abington Hall, Abington,
Cambridge CBI 6AH. England
Published in North America by ASM International.
The Materials Information Society, Materials Park,
Ohio 44073. USA
First published 1972, Butterworth & Co (Publishers) Ltd
Reprinted 1980
Second edition, 1986, Butterworth & Co (Publishers) Ltd
Third edition, 1993, Woodhead Publishing Ltd and ASM International
@ Woodhcad Publishing Ltd
Conditions of sale
All rights reserved. No part of this publication may be reproduccd or transmitted
in any form or by any means. electronic or mechanical, including photocopy,
recording. or any information storage and retrieval system. without permission in
writing from the publisher.
British Library Cataloguing in Publication Data
A catalogue rccord for this book is available from the British Library.
ISBN 1 85573 081 2
Designed by Geoff Green (text) and Chris Feely (jacket)
Typeset by Best-set Typesetter Ltd., Hong Kong
Printed by Hillman Printers (Frome) Ltd, Somerset, England
Contents
...
Preface to first edition Vlll
Preface to second edition X
Preface to third edition xii
1 Introduction and historical review 1
History of nickel plating 4
History of chromium plating 9
The future of nickel and chromium plating 11
2 Metallurgical aspects of electrodeposition 13
Methods of examination of stucture and surface
topography 13
3 Electroplating baths and anodes used for industrial nickel
deposition 41
Plating baths 41
Anodes for nickel plating 47
Barrel nickel plating 57
Health hazards caused by nickel plating 61
4 Engineering applications 66
Applications of thick electrodeposits 66
Chromium electrodeposits 89
5 Bright nickel electroplating 96
Brighteners 96
Properties of electrodeposited bright nickel 104
Properties of bright nickel baths 112
The incorporation and effect of organic addition agents 116
6 Control and purification of nickel electroplating solutions 132
Control of inorganic constituents 132
Control of organic constituents 133
Common contaminants of nickel plating baths 135
vi Contents
Effect of metallic contamination on structure and
properties of nickel deposits 139
Analysis for inorganic impurities 152
Removal of metallic contamination 153
Types of organic contamination 155
Filtration of electroplating baths 158
7 Physical and mechanical properties of electrodeposits and
methods of determination 162
Ductility 162
Adhesion 169
Stress 180
Hardness and wear resistance 194
Assessment of surface quality - brightness, reflectivity
and surface roughness 198
8 Chromium plating 205
The mechanism of deposition from chromic acid plating
baths 206
Baths based on chromic acid 207
Electrodeposition from trivalent baths 224
Stress in chromium deposits 230
Barrel chromium plating 238
Health hazards of chromium plating 240
9 Thickness and corrosion testing of nickel plus chromium
coatings 245
Thickness testing 245
Corrosion testing 25 1
Methods of evaluation of corrosion results 257
10 Decorative nickel plus chromium coating combinations 270
Multi-layer nickel coatings 273
Satin nickel 28 1
Modification of the chromium layer 282
Evaluation of corrosion resistance of nickel plus
chromium coatings 296
Corrosion resistance of deformed nickel plus chromium
coatings 302
11 Autocatalytic deposition of nickel 310
Phosphorus alloys 314
Pure autocatalytic nickel 323
Autocatalytic nickel coatings with non-metallic inclusions 324
Contents vii
12 Electroplating onto plastics 330
Electroplating onto plastics other than ABS 341
Testing of plated plastics 344
13 Deposition of nickel alloys 363
Nickelkobalt alloys 368
Nickelhron alloys 369
Nickelkin alloys 373
Nickel/molybdenum and nickelhungsten alloys 374
Nickel/phosphorus alloys 376
Autocatalytic nickel polyalloys 376
Nickellmanganese alloys 377
Nickelkhromium alloys 378
Nickelhndium alloys 379
Nickelkopper alloys 379
Miscellaneous alloys 380
14 Plating on difficult-to-plate metals 390
Aluminium 390
Preparation of uncommon metals for nickel plating 411
15 High-speed plating 423
Electrochemical factors 423
Plating solution composition 427
Methods used to increase the rate of deposition 427
Brush plating 433
Abrasive plating 436
Properties of deposits plated at high current density 438
Index 442
Preface to the first edition
This book is written for scientists, technologists and students who may
have diverse backgrounds but who wish to acquire a knowledge of the
fundamentals on which the important industrial processes of nickel and
chromium plating are based. Its scope includes descriptions of the meth-
ods of deposition and the properties of the coatings of these metals
obtained from aqueous solutions (with or without electric current) and
either applied individually or superimposed. (The latter is the case for
most of the ‘chrome’ plating that is carried out today.) The emphasis is
placed on the modern techniques employed for the deposition of these
metals, whether it is for decoration, corrosion protection or engineering
applications. However, obsolete processes are briefly described in the first
chapter, which it is felt makes an essential and interesting introduction to
current practice.
We hope that scientists who are already working in this field will
find our review of this modern technology to be of assistance to them,
whether they are in fundamental or applied research, or employed in the
industry. It must be pointed out that the book is intended to provide
information of a standard that is also suitable for undergraduates reading
for degrees in industrial metallurgy or chemistry and graduates taking
specialized M.Sc. courses in corrosion and protection; it is not meant to
serve as a practical handbook to give shop-floor guidance on how to
prepare and operate production plating baths. It will also be of assistance
to students studying for qualifications awarded by bodies such as the
Institute of Metal Finishing, Institution of Corrosion Technology, Royal
Institute of Chemistry and Institution of Metallurgists. We have therefore
included chemical, electrochemical and metallurgical theory where such
knowledge is essential to the full understanding of the processes described.
The most significant features of the organic compounds added to produce
bright nickel plate are summarized in Appendix 1, so that the effect of
these addition agents can be understood more easily by the reader, who
otherwise could be confused by the proprietary nature of these processes
and the large number of patents in existence. Those involved in produc-
tion plating should derive considerable help from the detailed descrip-
tions and critical comparisons of alternative plating processes now available
and of the control techniques that can be used for the solutions and the
Preface to first edition ix
coatings they produce. The analytical appendix should assist those plating
in either 1 litre beakers or 1OOOgal vats. In view of the arrival of SI units,
these have been used wherever possible, but have been slightly adapted
where it seemed desirable.
Our main reason for writing this book was to fill a gap that we felt
existed in metal-finishing literature. We considered that there was no up-
to-date English text dealing with both nickel and chromium plating,
except from the operational approach. This might well encourage new-
comers to the field to consider it to be more an art than a science.
The subject matter of this book has been included in some previous
publications, but it has usually been treated in a limited manner based
mainly on the particular scientific discipline in which the author was
trained. Metal deposition does not fit neatly into the sphere of any pure
science, for it is concerned both with the properties of the electrolyte
solution (chemistry) and of the metal deposit (metallurgy) and, of course,
the process of obtaining one from the other (electrochemistry). We con-
sidered that our experience could be combined to enable us to write a
text suitable not only for those first encountering this technology but also
for those experienced in the field, by reviewing, as far as possible, all of
the most important information published in widely scattered papers,
including very recent ones. Some unpublished work and many new optical
and electron photomicrographs are also included.
We hope that we have achieved our aim of providing our readers with
the opportunity of obtaining in one book detailed scientific information
on nickel and chromium plating, previously available only in scattered
and unconnected texts.
We are most grateful to those colleagues who aided us by supplying
information, assisting with photographic work or taking part in helpful
discussions. We also wish to thank all those organizations who supplied or
allowed us to reproduce illustrations and graphs. Reference to their
original source is given in the captions or accompanying text. However,
we are particularly grateful to the following for their permission to
include a number of figures that were originally published by them:
American Electroplaters’ Society
Electroplating and Metal Finishing
Institute of Metal Finishing
International Nickel Co. Ltd.
Metalloberfliche
W. Canning and Co. Ltd.
Particular thanks are due to Dr L.L. Shrier who first realized the need for
this book and who subsequently carried out a critical perusal of the
manuscript.
J.K.D.
T.E.S.
Preface to the second edition
A most far-reaching change to the nickel and chromium electroplating
industry has occurred since 1972. This is the vast decrease in the usage of
bright nickel plus chromium electrodeposits for decorative purposes on
vehicles and many other consumer-durables. However, this is partly com-
pensated by the increasing use of nickel plate for all kinds of engineering
applications.
Therefore, we have not merely updated the first edition but have also
placed additional emphasis on certain methods that have achieved more
industrial use in the 14 years since the first edition was published. This is
particularly the case for autocatalytic (electroless) nickel deposition and
for nickel plating onto aluminium and other difficult substrates and to a
lesser extent to plating onto plastics and high-speed plating. Each of these
is now the subject of a separate chapter. Also, since the first edition was
published, the deposition of various nickel alloys has expanded greatly,
both for decorative and functional applications, and so a new chapter
on this topic was felt to be essential. Other topics, such as composite
coatings and tampon (brush) plating, are now included, for although only
forming a very small proportion of the total quantity of the nickel plated
annually, they are usually employed for very demanding applications, for
which other techniques may not be suitable.
The inclusion of this extra material has obviously lengthened the book.
It would have been even longer, if some material from the first edition
had not been deleted. The former Chapter 2 and the Appendices have,
therefore, been eliminated. The majority of Chapter 2 was concerned
with the electrochemistry of electrodeposition from aqueous electrolyte
solutions, and this information is available in many other textbooks. The
subject matter of Appendix 1 can be obtained and updated by anyone
who wishes to study published Patents, while analytical methods of
Appendix 2 are contained in books and papers dealing with this subject.
The properties of the metals listed in Appendix 3 are given in many
standard reference works.
We hope that those new to the plating industry will find this book to be
of assistance and that those experienced in the industry will find its
revised version enables them to keep up-to-date with the latest develop-
ments in this specialized technology.