Metal dissolution and maximum stress during SCC process of ferritic (type 430) and austenitic (type 304 and type 316) stainless steels in acidic chloride solutions under constant applied stress

Abstract

By using a constant load method and inductive coupled plasma (ICP) spectrometer, the metal dissolution and maximum stress ( σ m air) of type 430 ferritic stainless, and type 304 and type 316 austenitic stainless steels during stress corrosion cracking (SCC) process were investigated under a constant applied stress condition in 0.82 kmol/m 3 hydrochloric acid (HCl) and 0.82 kmol/m 3 acidic chloride (pH 1.0) solutions. The σ m air of the specimens interrupted at various elongations up to failure under the same constant applied stress condition was measured at room temperature and air atmosphere by using an Instron type tensile machine. The metal dissolution behaviour of the stainless steels changed at the transition time ( t ss) in the corrosion elongation curve; that is, the dissolution rate before t ss was larger than that after t ss. The σ m air decreased gradually with increasing elongation, but showed a rapid small reduction at t ss and then decreased with elongation with a sudden reduction around fracture. The results obtained were discussed in terms of the amount of metal ions per the number of cracks, selective dissolution, reduction in cross sectional area and so on.