Effect of Cu on corrosion evolution for Fe-8.5Al-30Mn-1C low-density steel: insights from bipolar electrochemistry testing

Low-density steels have gained increasing popularity in industrial applications. However, their corrosion mechanisms remain insufficiently studied. This study aims to investigate the influence of varying Cu content on the microstructure evolution and corrosion resistance of Fe-8.5Al-30Mn-1C low-density steel. Potentio-dynamic polarization tests were conducted to evaluate the critical pitting potential (Epit) at varying Cu contents (0–3 Wt.%). In addition, bipolar electrochemistry was used to investigate the corrosion evolution at different potentials and the susceptibility of pit nucleation sites in low-density steel. The results indicate that the Epit remains unaffected by Cu content, as pit nucleation predominantly occurs at the interfaces between micro-scale carbides and the steel matrix – a process independent of Cu concentration. Although Cu promotes the formation of a corrosion film on the low-density steel, the potential for film formation exceeds that of pitting initiation. Furthermore, the resulting corrosion films exhibit insufficient stability and thickness to enhance pitting resistance. Consequently, Cu alloying does not improve pitting corrosion in low-density steel. This study elucidates the influence of Cu on corrosion mechanisms in low-density steel. The findings provide valuable insights for selecting optimal alloying elements to enhance pitting corrosion resistance in low-density steels. Furthermore, the results establish fundamental guidelines for developing highly corrosion-resistant surface films through controlled alloy design.