Influence of Addition of Nano-particles on Corrosion Resistance of Ni-P-Al₂O₃ Composite Coatings

Ni-P-Al2O3 composite coatings on aluminum alloy were prepared by electroless composite plating. The influence of the addition of nano-Al2O3 particles on the corrosion resistance of composite coatings was studied by electrochemical tests and salt spray test. The surface morphology of coatings was observed with scanning electron microscopy (SEM).The chemical composition was analyzed by EDS. The thickness of composite coatings was measured by X-ray fluorescence thickness gauge. The results indicate that the addition of nano-Al2O3 in solution has optimum values of about 2~3 g·L-1 by using dispersion method of magnetic stirring. The composite coating obtained can protect aluminum alloy from corroding for more than 48h in the salt spray test, and the corrosion morphology is more uniform after immersion in 5%NaCl solution in 35 ℃.