Abstract
The difference in stress corrosion cracking (SCC) susceptibility between high and low interstitial ferritic stainless steels (SS) (26Cr-1Mo) in chloride solutions is the result of the relation between their corrosion and cracking potentials. Changes in the initial state of a normally immune low interstitial steel (E-Brite)) either by heat treatment or prior deformation will induce susceptibility to SCC. On loading, transient creep produced breaks in the protective film in the form of corrosion trenches. However, there is an induction period for crack initiation, rationalized by the necessity to attain the critical degree of occlusion in the trenches. E-Brite, in a condition susceptible to SCC displayed substantially higher slip steps as compared to the immune mill-annealed state. Low temperature annealing of the deformed susceptible condition reduced the slip step heights and correspondingly restored immunity. The difference in SCC behavior of the high and low interstitial alloys at the corrosion potential resides primarily in the relative corrosion and repassivation rates of each material.
