Enhanced pitting resistance and antibacterial durability of Cu-bearing stainless steels via tailoring Cu distributions

Abstract

The addition of Cu to stainless steel has been demonstrated to enhance antimicrobial properties, however, its distribution state can significantly affect corrosion resistance and antimicrobial durability. In this work, the influence of Cu distribution state within microstructures (solid solution versus segregated into precipitates) on corrosion resistance and antimicrobial properties was investigated using a 4 wt.% Cu-bearing stainless steel. Corrosion resistance assessed using both electrochemical and immersion tests, showed that material with Cu in solid solution exhibited enhanced pitting resistance and comparable antimicrobial properties in comparison to aged samples that contained Cu-precipitates. Antimicrobial tests demonstrated that after 24 h of exposure to material surfaces, Escherichia coli microbial numbers were reduced by greater than 90% at both Cu states, which was attributed to a synergistic effect of interaction between bacteria and Cu-doped surfaces, and high concentrations of released Cu ions in surrounding fluid. Solution-treated SS-Cu exhibited a release capability of Cu ions comparable to aged Cu-bearing stainless steel, with Cu enrichment within the passive film considered as the source of discharged Cu ions. This characteristic endows solution-treated Cu-bearing stainless steel with the potential of releasing Cu ions durably.