Leakage Reason of 0Cr18Ni9 Stainless Steel Natural Gas Pipeline

0Cr18Ni9 seamless steel pipe was used in an offshore natural gas transmission pipeline. After the installation of the pipeline, a leakage was found during the water pressure test. The leaked natural gas pipeline was analyzed by direct reading spectrometer, tensile testing machine, optical metallurgical microscopy, scanning electron microscopy and other analysis methods. The results show that the metallurgical quality of the leaked pipeline met the technical requirements, but there was a warped skin on the inner surface of the pipeline, and crevice corrosion occurred between the warped skin and the substrate, resulting in the pipeline perforation and leakage.