A DIRECT ELECTROLESS PLATING PROCESS OF AZ91D MAGNESIUM ALLOYS

Using H3PO4+KF for acid pickle pretreatment and 2NiCO3·3Ni(OH)2·4H2O as the main salt for electroless plating,direct electroless Ni-P plating on AZ91D magnesium alloy from a plating bath containing nickel carbonate was investigated.The morphology and microstructure of the electroless Ni-P coating were studied by using SEM.The electroless Ni-P coating was compact and non obvious defects.The micro-hardness of Ni-P coatings were 400 HV~500 HV and the phosphorus content of this coating was about 8.56 wt.%.The deposition rate of the electroless Ni-P alloy was about 0.3 μm/min.The acid pickle pretreatment on the AZ91D magnesium alloy substrate provides surface pits to act as sites for mechanical interlocking to improve adhesion of the coating.