Effect of heat treatment on tribocorrosion of nanostructure Ni-P coatings

High phosphorus Ni-P coatings were deposited on mild steel by electroless plating, and then, they were isothermally heat treated at 400°C (HT400) and 600°C (HT600) for 1 h. The electrochemical behaviour of the coatings was evaluated by potentiodynamic polarisation technique in 3.5 wt-%NaCl solution. Tribocorrosion tests were also carried out in 3.5 wt-%NaCl solution. Scanning electron microscopy and three-dimensional profilometry were used to study the wear scars. The results showed that the maximum tribocorrosion resistance was obtained for heat treated Ni-P coating at 600°C because of higher corrosion resistance of HT600 than that of HT400 and also higher hardness of HT600 than that of as plated coating. Moreover, the lowest friction coefficient was achieved for HT600 coating.