Chloride-Induced Degradation of Zeron® 100 Super Duplex Stainless Steel: Critical Temperatures and Potentials for Pit and Crevice Corrosion

High chloride concentrations in industrial brines, such as those encountered in lithium extraction, critically challenge the localized corrosion resistance of structural alloys. This study investigates the effect of chloride concentration on the corrosion behavior of Zeron® 100 super duplex stainless steel (UNS S32760) by evaluating critical pitting temperature (CPT), critical crevice temperature (CCT), pitting potential ( E pit ), and crevice repassivation potential ( E rep ) across a wide range of chloride concentrations (1–8 M). CPT, CCT, and E rep decreased logarithmically with chloride concentration, indicating a progressive reduction in localized corrosion resistance. At the highest Cl − concentrations, E rep falls below the corrosion potential, implying that spontaneous crevice corrosion is thermodynamically feasible under open-circuit conditions. SEM analysis reveals that increasing chloride concentration alters pit morphology and reduces the protective nature of the lacy cover. These findings provide new insights into the degradation mechanisms of Zeron® 100 in chloride-rich environments and highlight the importance of considering E rep , in addition to CPT and E pit , when predicting long-term performance.