Effect of cerium content on passive film stability and pitting corrosion of super austenitic stainless steel in hypersaline seawater

Purpose This study aims to clarify the effect of cerium (Ce) content on passive film stability and localized corrosion behavior of a Cr-containing alloy in hypersaline seawater, with particular emphasis on the differences between aerated and deaerated conditions. Design/methodology/approach Alloys with different Ce contents were prepared and exposed to NaCl solutions with chloride concentrations up to 50,000 ppm under aerated and deaerated environments. Microstructural evolution and precipitation behavior were characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive spectroscopy. Corrosion behavior was evaluated using open-circuit potential, electrochemical impedance spectroscopy, potentiodynamic polarization, surface morphology analysis and X-ray photoelectron spectroscopy characterization of passive films. Findings Moderate Ce addition (0.5 Wt.%) significantly refines the microstructure, suppresses harmful precipitates and promotes the formation of compact, Cr-rich passive films, resulting in enhanced corrosion resistance under both aerated and deaerated conditions. Excessive Ce addition induces Ce-rich and Cr/Mo-rich precipitates, increasing electrochemical heterogeneity and accelerating pitting corrosion, especially in oxygen-deficient environments. Deaerated conditions markedly weaken passive film stability and facilitate chloride penetration, leading to more severe localized corrosion. Originality/value This work provides a systematic comparison of Ce-regulated corrosion mechanisms under aerated and deaerated conditions in hypersaline seawater, revealing the synergistic roles of microstructure, precipitation evolution and passive film chemistry in governing localized corrosion resistance.