304 Stainless steel oxidation in sulfate and sulfate + bicarbonate solutions

摘要: The electrochemical characterization of 304 stainless steel in 0.1–0.5m Na2SO4 and + NaHCO3 aqueous solutions at pH∼8 was done combination with SEM surface analysis. Passivation the film without any pitting events is observed for current–potential current–time experiments, no anodic current spikes, which are associated depassivation events, distinguishable above background level. However, pictures an electrode polarized potentials 0.4V show microscopic pit nucleation. Even when metal may be regarded as passive from a or characteristics, passivity not stable localized breakdown can still occur. ascribed to nucleation active inclusion sites. pits do grow even into metastable state but die through repassivation by salt precipitation immediately after birth. effect solubility salts electrolyte produced dissolution results that growth two distinct processes. importance solution composition protective bicarbonate ions also discussed.