Books and publications

itives such as polysiloxanes, polyacryl- lates and polyethylene and including the use of the former species in synthesizing block copolymers. To achieve a high impact strength it is necessary to have a well-dispersed second phase which bonds to the primary polymer to avoid disrup- tion during processing. With block copolymers the careful control of processing conditions is especially necessary.

The final chapter on polyimides opens with a general consideration of high-temperature polymers and a little about their chemistry and, most im- portant, processing. Normally these systems, because of their high cross-link density, tend to be very brittle and much work has been undertaken in attempts to improve their toughness, often based on the addition of rubber particles. In absolute terms the increases achieved are not great and care must be taken to avoid reducing the desirable thermo- mechanical performance. It appears that the successful toughening of epoxies by these means has not been completely translated to the higher thermal perfor- mance materials and the author concludes that further work, involving thermoplas- tics, is required.

Rubber Toughened Engineering Plas- tics is a very well-produced and detailed account of the current field which brings the reader up to date with the situation. Although I approached it from the view of fibre composites rather than bulk polymers I found, with a few minor exceptions, the treatment to be very clear and the editor and contributors are to be congratulated. The price is high, effectively putting the book beyond the means of most individuals, but libraries and institutions should buy copies. Is there any chance of a paperback version?

Reviewers, partly in an attempt to show that they have done their job, are allowed one or two quibbles. Mine concerns the diffuse nature of the frac- ture data throughout this volume. Users of polymers, or those who advise them, require a collection of ready informa- tion - indeed I have often found that some information, though not necessar- ily totally accurate, is to be preferred to none at all. Accordingly, it would have been very helpful to have had a summary detailing the types of materials considered, their notch sensitivity, the range of impact properties and works of fracture plus an estimate of the reduc- tion in properties due to toughening, which could be used in an initial assess- ment of the material recommended in a specific situation. Furthermore, such a summary would have shown up gaps in our knowledge very clearly. However, this is a minor criticism of an excellent book.

N. L. Haneox

Corrosion Resistance of Zinc and Zinc Alloys Corrosion Technology Series 6 Frank C. Porter Marcel Dekker, 1994, ISBN 0-8247- 9213-0, 528 pp, $185

I have read the whole of this book which is well written by a world author- ity. It is printed in the USA to a high standard and is easy to read with the copious data clearly arranged in 109 figures and 99 tables. Particularly useful is the comprehensive collection of over 1100 worldwide literature citations: these cover the field of corrosion of zinc and zinc alloys from the early work of the last century, Davy (1824) on cathodic protection, to the very latest publications in 1994. These references enable the reader to go back to the orig- inal publications to get more and exact details of the work.

Information about the corrosion resistance of zinc is of fundamental importance to all types of engineers including those involved in selection and design. It is interesting to note that over 50% of the world's production of zinc is now used to protect steel from corrosion. This application is particu- larly important in the car industry which uses 15 × 106 tons of zinc-coated steel every year. The benefit of this increased usage is illustrated by the fact that half the bodywork of mass- produced cars is zinc coated and the life expectancy has correspondingly risen from 8.6 years in 1965 to 13.9 years in 1980.

The theory of corrosion is explained together with the important variables which affect the rate of corrosion and consequently the life expectancy. The technical level is suitable for final-year undergraduate and postgraduate stud- ents in engineering and scientific disci- plines. It is also invaluable as a source of data on the corrosion resistance of zinc and zinc alloy coatings in a wide variety of environments for chemical, civil, design, manufacturing, materials, mechanical and metallurgical engineers. The book provides all the information to answer the questions 'How?' and 'Why?'

Care must be exercised, however, in applying the data because variations in the environment factors can have a marked effect. The first layers formed on zinc have an influence throughout corrosion life so that local changes can be very important. The usual corrosion rate in rural or urban atmospheres is low, in the range of 1 8/zm y 1, due to the formation of insoluble protective layers of corrosion product such as zinc carbonate and/or hydroxide on the surface of the zinc. The corrosion rate is very much higher in the vicinity of a coke plant (70 /zm y-l) or in steam

engine sheds (40 ~m y-l) due to the pollution and humidity giving non- protective zinc sulphate and/or chloride. In low chloride atmospheres a general guide to the effect of sulphur dioxide on the corrosion rate is a basic value of 0.5-2 /xm y-i plus 1 /xm for every 40 /xmg SO2/m 3.

The first chapter in the book consists of general considerations including the methods of applying zinc and zinc alloy coatings to steel, their properties and applications. The next section covers the application, cost and use of conversion and organic coatings to improve corro- sion resistance and finishes with the different types of corrosion and the various corrosion testing procedures and their significance.

The resistance to atmospheric corro- sion is a major topic so is comprehen- sively reviewed in a chapter of 160 pages. The first part gives data about corrosion rates in different atmospheres experienced throughout the world. The influence of the important parameters including humidity, rain, temperature, impurities (mainly sulphur dioxide and chlorides) and location is described. The use of zinc and protective coatings for steel under interior and exterior envi- ronments and also urban, industrial, marine and rural atmospheres is detailed. Corrosion rates of zinc coat- ings containing aluminium or iron are compared under different conditions together with the relative costs. The chapter finishes with interesting and diverse documented case histories: these illustrate the extensive use of zinc with many examples of coatings in good condition after 50+ years of exposure.

Resistance to aqueous corrosion is discussed in the next chapter in terms of the type of water, the effect of pH, hardness and dissolved ions. Conjoint effects are explained, e.g. in soft water with low carbonate as little as 80 mg 1 -l of chloride can cause quite severe corro- sion whereas in hard scale-forming water no corrosion occurs even with a higher concentration of 700 mg 1 1. The inhibiting effect of many dissolved substances is tabulated. Corrosion data are then given individually for distilled, rain, supply, natural, industrial process, sea and brackish water. Reasons are given to explain the differences in observed rates of corrosion, e.g. the weight loss of zinc in 30 g 1 -I NaC1 is 198 g m -2 in 14 days but only 4 g m 2 when 12 g 1 1 MgC12 is added. It is the presence of the magnesium ions which encourage the formation of scale that is largely responsible for the good resistance of sea water. Case histories of the successful use of zinc in supply, natural and sea water are then given.

The chapter on resistance to corro- sion in soil is relatively short (28

381 Materials & Design Volume 15 Number 6 1994

Books and publications

pages). Data on zinc in different soils are described and tabulated: there is, as usual, a correlation with soil resistivity and permeability to air and water. Wet soils with a low resistivity are very aggressive. Zinc anodes, grounding cells and reinforced e~rth are mentioned and case histories listed.

The final chapter covers other applications of zinc including organic and inorganic chemicals, building materi- als and coatings and, finally, fuels. Much useful data are included in 57 pages of tables and the relevant references are indicated. There is, of course, an index which is comprehensive and necessary.

The book should provide invaluable to professional engineers and consul- tants. It can be recommended to every academic, research institution and industry library but is probably too expensive for student ownership.

Robert Walker University of Surrey

Design Data for Reinforced Plastics: A Guide for Engineers and Designers N.L. Hancox and R.M. Mayer Chapman & Hall, 1994; ISBN 0-412- 49320-9, 326pp, £29.95

This book describes a directory of infor- mation and data on reinforced plastics. The book is intended to be a guide for engineers, particularly design engineers, in the field of reinforced plastics or poly- meric matrix composites, which are referred to simply as 'Composites', even though metal and ceramic matrix composites exist. In this book the rein- forced plastics described are limited to commonly used thermosetting resins such as polyester and epoxy, reinforced with glass, aramid and carbon fibres. The authors are practising specialists in their field; Dr Neil Hancox works for AEA Technology and Dr Rayner Mayer is a consultant with Sciotech.

The authors aim the book primarily at industry, but it could also be useful as an academic text, probably at postgrad- uate research level in materials science or engineering. The book has been written for engineers in general and not specifically for engineers in the compos- ites industry. For those not familar with reinforced plastics, the initial chapters of the book provide a useful introduction to the subject. These chapters may be skipped by the more experienced reader.

The book is very well structured with a logical sequence of self-contained chapters. It starts with a useful group of ancillary sections: layout and use of the book; acknowledgements to key contributors; trademarks and registered tradenames of holders at the time of

writing; glossary of regularly used terms in the industry; units and fabric nota- tion, which is useful because the major- ity of reinforced plastics are fabricated as well as laminated structures. These sections are short and well worth reading to establish the scope, context and layout of the information in the book, which is so important for the effective use of any data book. There are twelve chapters: Design Considera- tions; Materials Selection and data assessment; Properties; Mechanical properties of random and fabric-rein- forced resins; Mechanical properties of aligned fibre composites; Impact and fracture; Thermal and electrical proper- ties; Fire performance; Environmental effects; Creep and fatigue; Influence of processing on properties; and Quality assurance.

Chapters 1 to 3 describe fundamental design considerations, selection pro- cesses, and constituent properties of composite materials. These chapters are very useful to designers new to compos- ite materials, whose processing and properties are quite different from conventional metallic materials. Chapters 4 and 5 describe the short- term mechanical properties of compos- ites with random, fabric and aligned reinforcements. Chapters 6 to 10 describe the properties of composite materials associated with their perfor- mance, including impact, fracture, thermal, electrical, fire, environmental, creep and fatigue. Chapter 11 describes the influence of the major processing routes on the properties of composite materials. The final chapter (Chapter 12) describes the quality assurance aspects associated with the processing of composite materials.

The emphasis of the book is on breadth rather than depth of subject matter, but with a thorough description of most of the range of parameters likely to be handled by the designer of composites. For more detailed descrip- tions the reader needs to refer to the references. This is not seen as a problem but a strength of the book. To provide a comprehensive description of all the properties and processes of composites would call for a much larger and expen- sive book and make it more difficult to locate information quickly.

The first chapter on design considera- tions is a little misleading because it essentially describes the rationale for the book's layout and the behaviour of composite materials. As the book purports to be a guide for designers, an insight into the design process would have been useful. Its omission though does not spoil the text and a reference to Mayer's book Design with Reinforced Plastics, which describes the design process, is included. 'Design implica- tions', as a sub-section, appears in most sections of each chapter, but they are

very brief. There are also limited refer- ences to the literature on designing with composite materials and references to unpublished sources of information are often not useful and are difficult to follow up. A list of the organizations mentioned, possibly as an appendix, with their addresses and telephone numbers would have been useful to enable readers to follow up data sources.

The presentation of the book is very good with an attractive cover. As you would expect from a data book, there are a large number of figures and tables, although some of the graphs are on the small side. The book is supplied in cased form (essential to the durability of a data book), but it is still reasonably priced and good value for money. The style is clear and the information easy to locate with a detailed index. A nice feature is the use of locator keywords in the margins. This ease of access of infor- mation is critical as the design process is highly iterative and frequent reference to the book is likely.

The authors have achieved their aim to provide a useful condensation of disparate data into a convenient single volume. The book is a useful data source for specialists and non-specialists for designing with reinforced plastics. It will never completely replace the normal sources of design information such as trade literature, books, papers, manuals, standards and test reports. However, these data sources change frequently as new and improved materials and process are developed and new stan- dards and legislation are introduced. This book provides useful data for preliminary design work and a directory to other design data sources. For the future, it might be even more useful to have the information contained in the book accessible on a computer in the form of a CD-ROM.

K. L. Edwards Engineering Design Centre

University of Cambridge

382 Materials & Design Volume 15 Number 6 1994