Predicting the Initiation and Propagation of EAC by Identifying and Quantifying Unit Microprocesses

There is great interest today in predicting the course of stress corrosion cracking as it involves mainly the initiation and propagation stages although in total SCC involves the stages of initial conditions, precursors, incubation, slow growth, and rapid growth. There is a particular interest in such predictions in the nuclear industry where there is no past history for lives of up to 60-80 years. The present discussion addresses mainly the last three stages. While relatively simple views of mechanisms of SCC have been advocated in the past, none of these provide a priori predictions for the dependencies on the seven principal variables nor do any of these mechanisms account for the probabilistic nature of SCC. The purpose of this discussion is to identify the possibly important distinguishable nano and atomic processes that function critically to affect the last three stages of SCC. Such processes include metal-metal bonding, under potential deposition, hydrogen entry, vacancy formation, double layer repulsion, interaction of dislocations with each other and with surfaces, and similar. Such microprocesses are identified and their possible contributions to prediction are discussed.