Electroless Deposition of Ni-Cu-P Coatings Containing Nano-Al_2O_3 Particles and Study of Its Corrosion Protective Behaviour in 0.5 M H_2SO_4

摘要

Ni-Cu-Pano-Al_2O_3 composite coatings are prepared on mild steel from an alkaline electroless plating bath containing different concentrations of Al_2O_3 nanoparticles. The protective effect of codeposited nanoparticles on the corrosion behaviour of the coatings is studied in 0.5 M H_2SO_4 solution. The electrochemical methods, that is, electrochemical noise (ECN), electrochemical impedance spectroscopy (EIS), and polarization measurements, are used to characterize the corrosion properties of the coatings. The results show that the inclusion of nanosized particles leads to significant improvement of corrosion resistance of the coatings. The highest corrosion resistance is obtained at 20 ppm of nanoparticles concentration in the plating bath. The ECN measurements results are in good agreement with results obtained from two other electrochemical methods after trend removal. The SEM images prove that nano-Al_2O_3 particles were embedded in the Ni-Cu-P matrix and are dispersed uniformly on the coating surface.