Ni-P coating by acidic electroless plating on Zr-8Al alloy

Acid pickling,phosphating and acidic electroless plating were applied to Zr-8Al alloy and Ni-P plating coating about 15 μm thickness was prepared.The phases,microstructure,micro-hardness and polarization behavior in 3.5% NaCl solution of the plating coating were investigated.The results show that the pickling and phosphating promote the deposition of electroless Ni-P plating.The electroless Ni-P plating coating consists of amorphous and typical cellular structure.Compared with that of un-plated alloy,the micro-hardness of Ni-P plating coating is improved by 58% and the corrosion potential of Ni-P plating coating in 3.5%NaCl solution shifts positively.The plating coating still has cellular structure after corrosion polarization.Selective corrosion of Zr-8Al alloy is prevented,which indicates that the corrosion resistance of Zr-8Al alloy is improved after acidic electroless Ni-P plating.