New Findings on Intergranular Corrosion Mechanism of 445J2 Ultra-Pure Ferritic Stainless Steel

A criterion for characterizing the intergranular corrosion sensitivity of 445J2 ultra-pure ferritic stainless steel was established using microstructure analysis and electrochemical impedance spectroscopy (EIS). The differences in the characterization results for the intergranular corrosion sensitivity of 445J2 stainless steel by EIS and the double loop-electrochemical potentiokinetic reactivation test were analyzed. The Mo-rich intermetallic compound did not cause depleted chromium zones in the sensitization temperature range of 500°C to 700°C but caused a surrounding elastic stress field. It was determined that the intergranular corrosion in 445J2 is due to the elastic stress field caused by the precipitated phase.