Corrosion behavior of Cu-Ni-Fe-Mn-Cr alloy in 3.5 wt.% NaCl solution

A novel Cu-10Ni-1.7Fe-0.5Mn-0.2Cr alloy was fabricated and exposed to a neutral 3.5 wt% NaCl solution for various days. The corrosion performance, corrosion film, and corrosion mode of the alloy were investigated in detail. The results suggested that the average corrosion rate reduced from 0.082 mm/a for 1-d immersion sample to 0.037 mm/a for 30-d immersion sample. The reduction in corrosion rate was mainly attributed to the progressive thickness and densification of the corrosion film, leading to increasing the resistance of the corrosion film with the prolonged exposure time. Low-valent oxides and chlorinated compounds were generated over the 1-d immersion sample surface, while high-valent oxides and hydroxide compounds were developed over the 30-d immersion sample surface. The mature corrosion film typically composed of Cu2O, CuO, Cu2(OH)3Cl, γ-FeOOH, MnO2, and Cr2O3. Eventually, the alloys suffered from selective corrosion and intergranular corrosion after a long exposure time in NaCl solution.