Aluminum Co-Deposition via DC Magnetron Sputtering for Enhanced Pitting Resistance of Copper-Nickel Alloys

Abstract

To investigate the improvements in the resistance of Cu-Ni alloys to surface pitting corrosion, Cu-Ni thin films containing Al were fabricated via DC magnetron sputtering. The morphologies of the fabricated samples were obtained using a scanning electron microscopy, which yielded information on the crystal size and sample surface before and after corrosion tests. X-ray diffraction was employed for the structural characterization of the as-deposited films, and vibrational spectroscopy was used to verify the corrosion products. The corrosion behaviors of the Cu-Ni and Cu-Ni-Al samples were examined using electrochemical polarization and cyclic corrosion tests. The Al co-deposited samples showed a refined crystal size as compared to the Cu-Ni sample, suggesting that they are more susceptible to the formation of a passivation film. The corrosion current density of the Cu-Ni-Al was reduced, and the corrosion potential was lower than that without Al content. The negative shift in the corrosion potential of the Al-containing samples indicates that the Al2O3 film suppressed the cathodic reaction, resulting in a decrease in the corrosion rate. These results are consistent with the cyclic corrosion test results, in which no pitting corrosion is observed in the Cu-Ni-Al sample.