Enhanced pitting resistance of novel low-nickel austenitic stainless steel QN1803 compared to conventional 300-series grades in aggressive chloride environments

Rising nickel costs and supply risks have increased the demand for sustainable stainless steels that maintain corrosion resistance and structural reliability. QN1803 was developed as a lower-cost alternative to conventional austenitic grades by reducing nickel content and compensating with manganese and nitrogen. These alloying elements stabilize the austenitic phase, which is otherwise destabilized by nickel reduction, while maintaining or enhancing resistance to localized corrosion. The performance of QN1803 was evaluated under aggressive chloride conditions (2 mol∙L -1 NaCl) and compared to UNS S30400 and UNS . Electrochemical tests, including electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis, demonstrated that QN1803 forms a passive film with lower defect density and greater electronic stability. These characteristics accelerate repassivation and account for the alloy’s superior critical pitting temperature. Complementary immersion testing (ASTM G48) confirmed that QN1803 exhibits more restricted pit growth, even under sensitization, which typically promotes localized degradation. This behavior is attributed to nitrogen-induced stabilization of the Cr-rich inner layer and the absence of MnS inclusions, which are commonly associated with pit initiation in conventional steels. Collectively, these findings underscore the synergistic role of nitrogen and manganese in maintaining passive film integrity despite nickel reduction, establishing QN1803 as a sustainable, cost-effective, and high-performance alternative for components in aggressive industrial or marine environments.