Effects of Content of Al₂O₃ Particles and Heat Treatment on Corrosion Resistance of Ni-P-Al₂O₃ Composite Coatings

Ni-P-Al(2)O(3) composite coatings with the uniform distribution of Al(2)O(3) particles were prepared by adding Al(2)O(3) particles into Ni-P plating solution and adopting optimum plating process. The morphology and microstructure of the coatings were investigated by using SEM, EDS and XRD. Being immersed in 10 vol.% H(2)SO(4) solutions, the corrosion resistance of Ni-P-Al(2)O(3) composite coatings was tested. The results show that when the solubility of Al(2)O(3) particles in plating solution is 8 g/l, the corrosion resistance is best. Comparing with as-plated Ni-P-Al(2)O(3) composite coatings, the corrosion resistance of heat-treated Ni-P-Al(2)O(3) composite coatings decreases by raising the temperature to 300 degrees C and then increases by raising the temperature to 450 degrees C.