LAUSR

Abstract A DC electroplated Ni Mo coating in a citrate bath was used in this tribocorrosion study. The cylindrical specimen was tested in the block-on-ring configuration with immersion in 5 wt% NaCl solution and the applied overpotential ranging from open-circuit potential (OCP) to +600 mVSCE. The weight loss, composition and microstructure of the tested specimen were measured and examined. The polarization curve showed no passivation of corrosion film at high overpotential. Thus, a continuous increase of weight loss in simple corrosion with applied overpotential was observed. On the contrary, a minimum friction coefficient at +200 mVSCE was obtained due to the better oxide film lubrication and better liquid support from the enclosed pitted holes. The synergy effect of wear and corrosion on the weight loss of this Ni Mo alloy coating was found to be less dominant than its other Ni-alloy counterparts, such as Ni P, Ni W, and Ni-W-P. The passivation of the corrosion film was considered to be the main factor for this difference.