Study on the Passivation Film Characteristics and Electrochemical Response Mechanism of 13Cr in Chloride‐Containing Solutions Under Different Conditions

ABSTRACT Electrochemical measurements and surface characterization were used to investigate the passivation and pitting corrosion behavior of 13Cr stainless steel in CO 2 ‐saturated, deoxygenated, and oxygenated environments. The results showed that 13Cr had a higher general corrosion tendency in the CO 2 ‐saturated solution than in the other two environments. However, the passive film formed under the CO 2 ‐saturated condition, although thinner, was more compact and contained fewer ionic defects, resulting in stronger re‐passivation ability and lower local corrosion sensitivity. Surface analysis further indicated a higher Cr 2 O 3 content in this film, which improved its compactness, reduced defect density, and enhanced self‐healing ability. These characteristics effectively suppressed pit initiation and propagation, leading to improved pitting corrosion resistance. These findings provide insight into the effect of CO 2 on the passivation mechanism of martensitic stainless steels.