Process of electroless nickel plating on previously activated LY12 aluminum alloy

Five processes for pre-activation of the surface of aluminum alloys were studied as related to the brightness and adhesion strength of electroless Ni coating prepared subsequently.An alkaline bath formulation suitable for activation of LY12 aluminum alloy was determined as an alternative to zinc immersion treatment.The optimal bath composition and process conditions were obtained by orthogonal test as follows:nickel sulfate 25 g/L,sodium hypophosphite 22 g/L,sodium citrate 30 g/L,UDIQ561 stabilizing agent 2 mg/L,UDIQ563 composite additive 0.2 mg/L,UDIQ562 accelerating agent 1.2 g/L,temperature 90 °C and pH 4.8.The process features deposition rate of 3.50 mg/(cm2·h),coating microhardness of 130-160 kgf/mm2 and phosphorus content of 15wt%.The electroless nickel coatings produced by the process are compact,well-adhered and uniform.The process has advantages of simpleness and environmental friendliness.