An Introduction To Corrosion And Protection Of Metals

Corrosion may be defined as an unintentional attack on a material through reaction with a surrounding medium. The term can refer to a process or to the damage caused by such a process. According to this general definition, materials other than metals, such as ceramics, plastics or concrete, may also be subject to corrosion (or corrode). When no particular reference is made to the material, however, it is normally understood that a metal is being attacked. It is entirely in this limited sense that the term is used in this book. There are good reasons for treating the corrosion of metals separately, apart from deterioration or decay of other materials. Since metals have a high electric conductivity, their corrosion is usually of an electrochemical nature. The chemical deterioration of electrically non-conducting ma terials, such as plastics and ceramics, is governed by other physico-chemical principles. It is necessary to devote more attention to metallic corrosion nowadays than earlier, due to 1. An increased use of metals within all fields of technology. 2. The use for special applications, e.g. within the atomic energy field, of rare and expensive metals, whose preservation requires particular precautions. 3. A more corrosive environment due to the increasing pollution of air and water. 4. The use of metallic constructions of more slender dimensions which do not tolerate corrosive attacks to the same extent as did the heavy constructions used in the old days.

Introduction and Scope-During the last few decades, an enormous effort has been made to understand corrosion phenomena and their mechanisms, and to elucidate the causes that dramatically influence the service lifetime of metal materials. The performance of metal materials in aggressive environments is critical for a sustainable society. The failure of the material in service impacts the economy, the environment, health, and society. In this regard, corrosion-based economic losses due to maintenance, repair, and the replacement of existing structures and infrastructure account for up to 4% of gross domestic product (GDP) in well developed countries. One of the biggest issues in corrosion engineering is estimating service lifetime. Corrosion prediction has become very difficult, as there is no direct correlation with service lifetime and experimental lab results, usually as a result of discrepancies between accelerated testing and real corrosion processes. It is of major interest to forecast the impact of corrosion-based losses on society and the global economy, since existing structures and infrastructure are becoming old, and crucial decisions now need to be made to replace them. On the other hand, environmental protocols seek to reduce greenhouse effects. Therefore, low emission policies, in force, establish regulations for the next generation of materials and technologies. Advanced technologies and emergent materials will enable us to get through the next century. Great advances are currently in progress for the development of corrosion-resistant metal materials for different sectors, such as energy, transport, construction, and health. This Special Issue on the corrosion and protection of metals is focused on current trends in corrosion science, engineering, and technology, ranging from fundamental to applied research, thus covering subjects related to corrosion mechanisms and modelling, protection and inhibition processes, and mitigation strategies.

This textbook is intended for a one-semester course in corrosion science at the graduate or advanced undergraduate level. The approach is that of a physical chemist or materials scientist, and the text is geared toward students of chemistry, materials science, and engineering. This textbook should also be useful to practicing corrosion engineers or materials engineers who wish to enhance their understanding of the fundamental principles of corrosion science. It is assumed that the student or reader does not have a background in electrochemistry. However, the student or reader should have taken at least an undergraduate course in materials science or physical chemistry. More material is presented in the textbook than can be covered in a one-semester course, so the book is intended for both the classroom and as a source book for further use. This book grew out of classroom lectures which the author presented between 1982 and the present while a professorial lecturer at George Washington University, Washington, DC, where he organized and taught a graduate course on “Environmental Effects on Materials.” Additional material has been provided by over 30 years of experience in corrosion research, largely at the Naval Research Laboratory, Washington, DC and also at the Bethlehem Steel Company, Bethlehem, PA and as a Robert A. Welch Postdoctoral Fellow at the University of Texas. The text emphasizes basic principles of corrosion science which underpin extensions to practice.

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.