Comparative study on the electrochemical performance of the Cu-30Ni and Cu-20Zn-10Ni alloys

The electrochemical performance of the Cu-20Zn-10Ni alloy was compared with that of the Cu-30Ni alloy in a 3.5 wt.% sodium chloride solution. Electrochemical impedance spectroscopy (EIS) measurements show that, interestingly, both the increasing rates of the thickness and resistance of the passive film formed on the Cu-20Zn-10Ni alloy are larger than those of the passive film formed on the Cu-30Ni alloy during the immersion of the two alloys in the 3.5 wt.% NaCl solution. The passive film formed on the Cu-20Zn-10Ni alloy surface is found to have a higher resistance and thicker depth than that formed on the Cu-30Ni alloy surface after the immersion of the two alloys in the 3.5 wt.% NaCl solution for 120 h. To some extent, the Cu-20Zn-10Ni alloy could substitute for the Cu-30Ni alloy in a corrosive environment containing chloride ions. According to X-ray diffraction and scanning electron microscopy studies, the corrosion product films of the Cu-20Zn-10Ni alloy were found to consist of two layers, with the inner layer and the outer layer being composed of cuprous oxide and (Cu, Zn)2Cl(OH)3, respectively, while the corrosion product films of the Cu-30Ni alloy were found to consist mainly of (Cu, Ni)2Cl(OH)3.