Stress Corrosion Cracking of Type 321 Stainless Steels under Simulated Petrochemical Conditions Containing Thiosulfate and Chloride

Abstract

Abstract The susceptibility to stress corrosion cracking (SCC) of Type 321 (UNS S32100) stainless steel (SS) under simulated petrochemical conditions containing thiosulfate and chloride (20 wt% sodium chloride [NaCl] + 0.01 M sodium thiosulfate [Na2S2O3], pH = 2) was assessed using the slow strain rate tensile (SSRT) test and static load (U-bend) tests at the free corrosion potentials. In the SSRT, effects of environmental factors, such as chloride (Cl−) plus thiosulfate (S2O32−), Cl− concentration, solution pH, and temperature, on the susceptibility to SCC of Type 321 SS were critically examined. In addition, factorial design experiments using Yates's algorithm quantitatively estimated the individual and interactive effects of temperature, Cl− concentration, and solution pH on the SCC susceptibility of Type 321 SS. In the U-bend tests, specimens were immersed in an autoclave containing deaerated 20 wt% NaCl + 0.01 M Na2S2O3 aqueous solution (pH = 2) for 1,400 h at either 80°C or 300°C. Results of the SSR...