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

摘要

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 (HC1) 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.