Electroless nickel-phosphorous alloy plating at low temperature

Nickel-phosphorous alloys were prepared by electroless plating on A3 steel substrate at low temperature.The effects of the contents of composite complexing agent and additive in plating bath,temperature,and pH on deposition rate were studied to optimize the process parameters of electroless Ni-P alloy plating.The properties of the coating such as appearance,adhesion strength,corrosion resistance,and porosity were characterized.The optimal process parameters of electroless Ni-P plating are as follows:NiSO 4.6H 2 O 30 g/L,NaH 2 PO 2.H 2 O 30 g/L,sodium citrate 10 g/L,phytic acid 18 g/L,NaF 6 g/L,thioglycolic acid 0.6 g/L,temperature 50 ℃,pH 9.0,and proper amount of ammonia water as buffer.The Ni-P alloy coating obtained under the given conditions has excellent appearance,low porosity,high adhesion strength,and good corrosion resistance.