Corrosion performance of electroless Ni-P on polymer coating of MAO coated AZ31 magnesium alloy

A layer of nickel-phosphorus alloy was electroless plated on the surface of a polymer coating (epoxy resin) on a micro-arc oxidized AZ31 magnesium alloy without the common process of sensitization. The structure of the sample with a nickel plated coating on a polymer coating was investigated by a scanning electron microscope (SEM) and an energy dispersed X-ray spectroscope (EDS), and the corrosion resistance of polymer coated samples before and after electroless nickel plating was investigated by electrochemical techniques and immersion tests. The results show that an electroless nickel plated coating on the polymer coating of an MAO coated AZ31 magnesium alloy can not only improve its corrosion resistance, but also make it a metallic surface. The layered composite coating fails by its lifting up by the accumulated corrosion products beneath the MAO coating after a long time immersion.