Abstract
Abstract Passivation behavior and surface chemistry of 304 stainless steel in alkaline solution with different HCO 3 − /CO 3 2– concentrations are studied with a combined electrochemical and XPS analytical investigation. Cathodic and anodic reactions are inhibited and accelerated, respectively, attributed to the depletion of acceptable oxygen and variation of passive film properties. Increasing HCO 3 − /CO 3 2– concentration does not alter the bilayer structure but leads to an intensification in electric field strength and composition changes including enrichment of oxidized Cr, increase of Fe(II)/Fe(III) ratio, and decrease of OH − /O 2– ratio. Meanwhile, the film thickness is reduced and the point defect density is increased due to the enhanced film dissolution. High HCO 3 − /CO 3 2– concentration increases the critical chloride concentration of 304 SS in alkaline solution, attributed to the inhibition of the localized acidification within the pits and suppression of the stable pit development.
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