Failure analysis of corrosion perforation in stainless steel seamless pipes

A seamless steel pipe experienced leakage failure. No leaks were detected during the first water pressure test, but the second test revealed three pipe leak points. Samples were taken from the leakage areas, and the reasons for failure were determined by a team of experts through macroscopic observation, chemical composition analysis, tensile testing, metallographic structure analysis, and scanning electron microscopy analysis. The study found that the corrosion pits were primarily caused by elements introducing corrosive media, namely P, S, K, and Cl. Among these, the contents of S and Cl were relatively low. At the same time, the leading corrosive media were P and K. It was ultimately concluded that alkaline elements concentrated in the low-lying areas of the pipe created a strong alkaline environment, leading to alkaline corrosion perforation. Additionally, due to differences in corrosion potential, low melting point eutectic substances accumulated on the steel pipe, resulting in electrochemical corrosion that accelerated the rate of corrosion perforation.