Failure Analysis of 316L Pipeline in Chemical Plant

Rapid corrosion occurred to a semi-finished diesel pipeline made of 316L stainless steel at the bottom of the horizontal section, for 5 times within 9 months.The causes for the pipeline failure were analyzed by macroscopic analysis, chemical composition analysis, mechanical properties testing, metallographic analysis, corrosion product phase analysis, harmful phase analysis of corrosive media, and corrosion product analysis.The results show that the corrosion of the stainless-steel pipeline is oxygen corrosion and pitting corrosion.Corrosion products or impurities such as iron oxides flowed along the bottom of the pipeline with the media, leading to linear erosion wear on the bottom of the pipeline and damaging the protective effect of passivating film. As a result, the bottom of the pipeline was first corroded. Chlorine ions inthe corrosion environment can easily destroy the passivating film on the surface of stainless steel, forming pitting corrosion and becoming the active center of hole corrosion extension.