Abstract: A leakage occurred in the 2205 duplex stainless steel wastewater pipeline of a certain chemical plant. The causes of pipeline leakage were analyzed using macroscopic observation, chemical composition analysis, corrosion depth testing, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that the 2205 stainless steel pipeline experienced pitting corrosion, with many granular σ phases on the inner wall of the pipe, which reduced the pitting corrosion resistance of materials. Under acidic conditions and the action of chloridion, pitting corrosion pits emerged and rapidly developed, ultimately led to corrosion perforation of the pipeline.