A High Performance of ENi-P Coatings on Mechanical and Tribological Properties with Influence of Bath pH on AZ91 Magnesium Alloy

摘要

Electroless nickel-phosphorus (ENi-P) coating was carried out on AZ91 magnesium alloy substrates by varying the bath solutions pH. The ENi-P coating process was carried out with sodium hydroxide as the pH adjuster. The effect of bath pH values on surface characteristics and wear resistance properties were investigated after deposition on AZ91 magnesium alloy substrates. Three suitable bath compositions with different pH were prepared for coating the substrates. Encouraging results for ENi-P deposit were obtained when the bath pH value was maintained at 6.5. A smooth and uniform microstructure was observed in the deposit obtained from bath B (6.5 pH). It also enhanced the microhardness and wettability, while the surface roughness of the ENi-P deposit reduced considerably, thereby resulting in better wear resistance and also preventing regular or early failures, and improving service life.