Effect of HCl on Pickling of 304 Stainless Steel in Iron Chloride-Based Electrolytes

Abstract Weight loss and corrosion potential measurements were performed to understand the role of HCl in the pickling of oxidized 304 stainless steel in HCl-FeCl 3 -FeCl 2 electrolytes. The surface finish was analyzed with SEM-EDX. The oxidized material is active on immersion, resulting in a low corrosion potential and a high weight loss. After certain duration the material either remains active or passive depending on the HCl content. At low contents, an ongoing active-to-passive transition results in localized corrosion at pits, grain boundaries and honeycombed recesses. The corrosion potential becomes high and the weight loss is suppressed. The weight loss decreases in initial stage and rises on extended pickling with adding HCl. Because of surface brightening, the material is always active at concentrated HCl.