Stress Corrosion Cracking Susceptibility of Stainless Steel 321 in Chloride - Hydrogen Sulfide Media

Abstract Stabilized stainless steel (SS) grade 321 has been widely used in the petroleum refining and petrochemical industries for applications in hydrocarbon streams containing hydrogen sulfide. Factors such as corrosive media, process conditions, manufacturing conditions and metallurgical structure affect the performance of 321 SS equipment and piping in process industry streams. Though, 321 SS equipment have been performing well in process industry streams, there are reports of equipment failure due to corrosion and stress corrosion cracking (SCC). Studies of the failures of 321 SS process equipment led to the believe that the synergistic action of hydrogen sulfide and chloride may be playing a role in some of the equipment failures. In the present paper, the results of a study on the effects of chloride-hydrogen sulfide synergism on SCC susceptibility of 321 SS are presented. The SS 321 was evaluated for their susceptibility to SCC in solutions containing chloride and thiosulfate by slow strain rate testing (SSRT). The study revealed that the SCC susceptibility of 321 SS is strongly influenced by chloride - hydrogen sulfide synergism.