Effects of different plating modes on microstructure and corrosion resistance of Ni-Cu alloy coatings

摘要

The aim of the work is to study the effects of different plating modes on the microstructure and corrosion resistance of Ni-Cu alloy coatings. Ni-Cu alloy coatings were deposited by direct current (DC), pulse current (PC) and pulse reverse current (PRC) methods, respectively. The surface morphology and the grain size were investigated by SEM and XRD. The corrosion resistance of the alloy coatings was evaluated in 3.5wt% NaCI solution by electrochemical impedance spectroscopy (EIS) technique and polarizing curves method. The results showed that the crystal grains of the alloy coatings prepared by DC, PC and PRC, respectively, became smaller and smaller in order, and the coating surface became compacter and smoother correspondingly. This was consistent with the surface morphology of the alloy coatings. The results of EIS and polarizing curve tests showed that the corrosion resistance of Ni Cu alloy coatings deposited by PRC method was the best, and then by PC and DC in sequence. The corrosion resistance of the alloy coatings depended on the alloy structure and composition, the best corrosion resistance of the Ni-Cu alloy coatings deposited by PRC was attributed to its fining of the crystal grains and the dense structure.