Optimization of Technology of Electroless Ni-P Pretreatment Process on the Aluminum Alloy Surface

The electroless Ni-P coating could improve the defects of aluminum alloy such as intercrystalline corrosion occurred easily,low surface hardness,poor abrasion resistance.To obtain good combination force of the coating and aluminum substrate the pre-treatment process is even more important.Analyzed by orthogonal tests and maximum difference method,the important orders that the processing parameters of activation and pre-nickel plating affect the subsequent electroless plating Ni-P plating rate are determined.The optimal formula and processing conditions of activation and pre-nickel plating were also determined.The morphology and properties of the coatings obtained by activation and pre-nickel plating were investigated by metallographic microscope,scanning electron microscope,weight gain and loss method and thermal shock tests.Experimental results show that: the new activation and pre-electroless technology can significantly improve the microhardness,deposition rate and bonding strength with the substrate of Ni-P coating.The coating obtained as such has dense and homogenous microstructures and good corrosion resistance.