Influence of pretreatment on property of electroless plating of Ni-P on aluminum surface

Aiming at the disadvantages of aluminum alloy,such as vulnerable to intercrystalline corrosion,low surface hardness,poor abrasion resistance,electroless plating of Ni-P on aluminum surface was studied.The deposition rate,microhardness,bond strength and corrosion resistance were measured with metallographic microscope,SEM energy spectrum analysis,mass-increase method,thermal shock test and grid test,mass-loss method to determine the effect of the parameters of nickel-phosphorus alloy electroless plating process and the time of pre-electroless plating and activation process.The pre-electroless plating process used NiSO4 as main salt,NaH2PO2 as reducing agent and Na4P2O7 as complexing agent.The results showed that the new activation and pre-electroless plating process could significantly improve the bond strength of Ni-P coating and substrate.The highest deposition rate could be achieved.At the same time,the organizational structure of the coatings was dense and uniform,with good hardness,and excellent corrosion resistance.