Corrosion Resistance of X70 LSAW Pipe with Heavy Wall Used for Oil and Gas Transportation in Deep Sea

X70 longitudinal submerged arc welded (LSAW) pipe with heavy wall used for oil and gas transportation in deep sea (1 016 mm,wall thickness of 36.5 mm) was developed and produced. The chemical composition,microstructure and mechanical properties of the pipeline steel were analyzed,and the corrosion resistance of the pipe body and welded joint was studied through hydrogen induced cracking (HIC),sulfide stress corrosion (SSC) and corrosion immersion tests. The results show that the body and welded joint of the X70 LSAW pipe had good resistance to hydrogen-induced cracking and sulfide stress corrosion cracking,and their corrosion rates were all less than 0.09 mm/a,which means that the X70 LSAW pipe can be used in corrosive marine environment.