Whitney Award Lecture—1985: On The Roles of Corrosion Products in Local Cell Processes

This paper reviews work performed in the author’s laboratory on the roles that corrosion products play in corrosion and materials degradation processes. Subject areas include the following: (1) wedging action, in which the tensile stresses required for crack propagation are generated by the formation of solid corrosion products within the crack cavity; (2) gas bubble formation and coalescence that eventually fills a major volume segment of a pit, crevice, or crack; (3) an experimental determination and mathematical modeling of the local electrode potential and solution composition existing within active pits and crevices; (4) an analysis that shows the existence of a limiting electrode potential (ELIM) in a cavity and defines its value; (5) and an analysis based on the ELIM concept and on known trends in concentrations of ionic species that provides a means for distinguishing between stress corrosion cracking (SCC) and hydrogen cracking (HC) in noble metal alloys.