The generation of corrosion under insulation and stress corrosion cracking due to sulphide stress cracking in an austenitic stainless steel hydrocarbon gas pipeline

This paper describes a root cause failure investigation of a corroded AISI 304L stainless steel pipeline used to carry hydrocarbon gas. The corrosion was originally identified due to a leakage observed after removal of a section of lagging insulation. The investigation revealed however a three stage mechanism of attack had occurred; both intergranular cracking and transgranular cracking was present originating from both the internal and external surfaces. The process of attack occurred due to SSC from the internal surface resulting in CUI; the attack to the external surface then initiated SCC. A complex process of corrosion mechanisms was initially attributed to CUI, it was however due to internally initiated corrosion due to the combination of water carryover and the presence of corrosive species highlighting the importance of forensic examinations in oil and gas failures.