Effects of copper on localized corrosion behavior of stainless steel 304 in 3.5 wt.% NaCl solution

• Corrosion behaviour of 304Cu was studied with a focus on inclusions and passive films. • Only MnS dissolved during metastable pitting. • Copper dissolution could promote pit formation. Copper (Cu) is often added into stainless steel to enhance their antimicrobial properties, though the effects of Cu on its corrosion resistance remain unclear. To investigate the influence of Cu on pitting behavior of stainless steel 304, a comprehensive study was conducted with electrochemical techniques, scanning electron microscopy, and X-ray photoelectron spectroscopy. Potentiostatic polarization measurements reveal that the addition of Cu affected the preferential dissolution of inclusions during both metastable and stable pitting. Additionally, Cu addition alters the composition and thickness of passive film, and thereby influenced corrosion behavior of stainless steel 304.