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

摘要

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