Study of electroless Ni plating with palladium-free activation on the surface of SiC_p/Al composites

The direct palladium-free activation is used to render the surface of SiC_p/Al composites higher active in order to obtain glossy and uniform Ni-P film with excellent adhesive strength to the substrate. The morphology and the elemental compositions of the coatings and the specimens before and after activation are clarified by the scanning electron microscopy and X-ray energy dispersive spectrometer. Influences of the activation factors such as time, ultrasonic, the temperature and time of the heat treatment on the coating quality, adhesion and deposition rate are investigated. The optimal pretreatment conditions are obtained to deposit nickel on the surface of the SiC_p/Al composites reinforced with 70 volume percent fine particulate silicon carbide. Results show that the optimal palladium-free activation conditions are obtained, with palladium-free activation for 9 min under ultrasonic, then heat treatment at 170°C for 20 min, and the solution contains Ni(Ac)₂(g), NaH₂PO₂(g), CH₃CH₂OH (ml) and H₂O(ml) in proportion of 1:1:15:2. The Ni-P activated film which has high catalysis for electroless Ni plating covers the composites surface after the palladium-free activation.