Effects of Plating Bath Composition and Operating Condition on Properties of Electroless Coating for High Strength Aluminum Alloy

The table of L9 (34) of orthogonal design was adopted in the experiment. The optimal formulation and process conditions of electroless nickel plating on high strength aluminum alloy were determined. The influences of bath composition and operating conditions on the hardness and deposition rate were analyzed and discussed. The experimental results show that the optimal plating formulation were obtained, which were consisted of nickel sulfate hexahydrate(25g/L), sodium hypophosphite(20g/L) and sodium acetate(15g/L). The operating conditions are as follows: 80~85°C, pH value 5.0. The coating structure is more homogenous and compact, and the coating has good brightness. Meanwhile, the hardness is up to 376.8HV, and the deposition rate is 17.2μm/h. The order of effects on hardness is pH value, sodium acetate, sodium hypophosphite and nickel sulfate concentration in turn. The hardness of coating decreased after heat treatment on low temperature. When the temperature exceed 200°C, the hardness increased with temperature rising and reached the peak value at 400°C(565.3HV).