Effect of S^2-on Corrosion Resistance of Cu-7Ni-3Al Alloy in NaCl Solutions

Cu-7Ni-3Al copper alloy is prepared by vacuum smelting based on the copper-nickel corrosion-resistant copper alloys. The corrosion rate and corrosion pattern of Cu-7Ni-3Al alloy in 3.5% (w) NaCl solutions with different concentrations of S^2- are analyzed by the static total impregnation corrosion experiment. The results show that Cu-7Ni-3Al alloy with good comprehensive performance is prepared by vacuum smelting. The existence of S^2- promotes the corrosion of Cu-7Ni-3Al alloy. The corrosion rate of Cu-7Ni-3Al alloy increases with the increase of S^2-concentration, because in the environment of S^2-, Cu-7Ni-3Al alloys will form Cu₂S, and Cu₂S will make the passivated film brittle and prevent the formation of oxide film, thus accelerating corrosion. Therefore, the corrosion resistance of Cu-7Ni-3Al alloy decreases with the increase of S^2-content in 3.5% NaCl solution.