Passivity And Protection Of Metals Against Corrosion

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.

Electrocorrosion, the corrosion of metallic constructions by external currents, is the most significant factor in conductive aggressive environments. Corrosion of underground and underwater metal constructions by stray currents has been comprehensively studied in the past decades and is considered here only in the form of a review. The primary attention is on corrosion, by external anodic (mainly) and cathodic currents, of metal constructions in the highly aggressive environments typical for electrochemical plants, where penetration of the external currents (leakage currents) from the electrolytic baths into metal constructions is unavoidable. A new approach to the problem of electrocorrosion protection of passive structural metals is considered in this book, keeping the metals attacked by external currents in the boundaries of their passive field. The systems, developed in accordance with this approach, are based on the modification of existing and elaboration of new methods of electrocorrosion protection. These systems take into account corrosion and electrochemical characteristics of the aggressive media (redox potential, conductivity etc.) and of the passive metal (corrosion and activation potentials, current density in a passive state, etc) as well as the sizes and distribution character of the external currents. The book covers analysis of leakage current distributions in electrochemical plants, their influence, methods to estimate corrosion stability of metallic structures subject to external currents and presents many concrete examples of the successful introduction of corrosion protection systems in operating plants. A new approach to protection from electrocorrosion, taking into account the passive state of the metal in aggressive media Newly developed and modifications of well known methods of electrocorrosion protection are presented. Systematized data on electrocorrosion and protection of metals, especially in electrochemical plants, allow corrosion engineers, researchers and personnel maintaining the equipment of electrochemical plants to analyze the corrosion state of metallic equipment and prevent electrocorrosion.

The objectives of this book are to give technical information about anodic pro tection, explain how economic analyses are made to determine whether or not it should be used, and describe some of the applications and equipment. Lim itations of the technique will be pointed out. Technological changes that have resulted in higher temperatures, pres sures, and velocities increase corrosion rates and markedly influence materials selection and design decisions. Continuous cycle systems impose increased demands on system reliability. New processes require more sophisticated equipment made of costlier metals which are often in short supply and subject to the vagaries of international commerce. The impact of continuing inflation influences decisions related to capital expenditures and maintenance costs. Some problems caused by these considerations can be solved, or solutions simplified, by the use of anodic protection. Technical and scientific information is presented on applications to industrial equipment, economics, design and installation, operation and maintenance, electrochemical principles, laboratory tests and procedures. A historical summary, patent list, glossary of terms, and a subject index are included. It is important to acknowledge that much of the information has been from the original work of others, including the publications of many friends.

The use of conducting polymers for the anticorrosion protection of metals has attracted great interest during the last 30 years. The design and development of conducting polymers-based coating systems with commercial viability is expected to be advanced by applying nanotechnology and has received substantial attention recently. This book begins with corrosion fundamentals and ends with an emphasis on developments made in conducting polymer science and technology using nanotechnology. Additionally, it gives a detailed account of experimental methods of corrosion testing.