Factors Influencing Plating Rate of Electroless Ni-P Plating and Optimization of the Plating Process

A series of test was carried out to investigate the effects of various factors such as pH value,temperature,and concentration of 2NiCO3·3Ni(OH)2·4H2O,NaH2PO2·H2O,and H8C6O3·H2O on the plating rate of electroless nickel plating for AZ91D magnesium alloys.The optimized parameters were obtained by taking into account the effects of those factors and by modifying the plating bath composition and plating parameters as well.The results showed that the composition of the plating solution and its pH-value and temperature had complex influences on the plating rate.The plating rate was not only related to the production efficiency but also had effects on the adhesion strength and performance of the electroless Ni coating.It was feasible to prepare uniform and compact electroless Ni-P deposits without any visible defects using the optimized plating process.The resulting Ni-P alloy coating contained 8.56% P and had a hardness of 460-520 HV,while it was well adhered to the Mg alloy substrate.