It is now time for a comprehensive treatise to look at the whole field of electrochemistry. The present treatise was conceived in 1974, and the earliest invitations to authors for contributions were made in 1975. The completion of the early been delayed by various factors. volumes has There has been no attempt to make each article emphasize the most recent situation at the expense of an overall statement of the modern view. This treatise is not a collection of articles from Recent Advances in Electrochemistry or Modern Aspects of Electrochemistry. It is an attempt at making a mature statement about the present position in the vast area of what is best looked at as a new interdisciplinary field. Texas A & M University J. O'M. Bockris University of Ottawa B. E. Conway Case Western Reserve University Ernest Yeager Texas A & M University Ralph E. White Preface to Volume 4 The science of degradation of materials involves a vast area of science and technology, the economic importance of which rivals that of any other clearly defined area affecting the standard of life. The basis of the corrosion process is the electrochemical charge-transfer reaction, and the center of the subject of the degradation of materials is electrochemical material science.