Effect of surfactant on the electrodeposition and wear resistance of Ni–Al2O3 composite coatings

Ni–Al2O3 composite coatings were electrodeposited from a Watts-type bath containing particles in suspension, which were dispersed with the aid of a cationic surfactant hexadecylpyridinium bromide (HPB). The effects of the surfactant on the zeta potential, co-deposition and distribution of Al2O3 particles in nickel matrix, and tribological properties of composite coatings were investigated. Experimental results showed that the addition of HPB could improve the amount of co-deposited Al2O3 particles, reduce the agglomeration of particles and achieve a more uniform distribution of Al2O3 particles in the nickel matrix. The wear resistance of the composite coatings increased with increasing concentration of HPB up to a certain optimum of 150 mg l−1, beyond which a decreasing trend of wear resistance was observed under dry sliding and oil-lubricated conditions. This is probably due to the increased brittleness of metal matrix when the concentration of surfactant exceeded the optimum.