Environmentally assisted cracking behavior of single and dual phase stainless steels in hot chloride solutions

The environmentally assisted cracking (EAC) behavior of AISI 316L austenitic stainless steel (SS), AISI 430 ferritic stainless steel and 22% Cr duplex stainless steel (DSS) in hot chloride solutions were investigated. Slow strain rate testing (SSRT) technique was employed to evaluate the susceptibility to EAC in 3.5 wt.% NaCl solution at 80 °C and in 40 wt.% CaCl2 solution at 100 °C. The experimental results showed that the resistances to localized corrosion and EAC were strongly dependent on the microstructure, chemical composition and the nature of the environment involved. 430 SS was found less resistant to pitting corrosion and EAC in both chloride solutions. The SSRT results indicated that 316L SS and 22% Cr DSS became susceptible to EAC in hot 40 wt.% CaCl2 solution. Selective dissolution was found participating in the initiation and growth processes in EAC of 22% Cr DSS. Besides, intergranular cracking was found in 316L austenitic SS while pitting enhanced EAC occurred in 430 ferritic SS in 40 wt.% CaCl2 solution at 100 °C. The effect of strain rate on the susceptibility to EAC in hot CaCl2 solution was more pronounced in 316L austenitic SS and 22% Cr DSS than that in 430 ferritic SS.