Investigation Of Electroless Nickel Plating On Magnesium Alloy In Nickel Acetate System

Magnesium alloys exhibit many attractive properties，such as high strengh-to-weightratio, high electromagnetic shieldlessness, good dampness, good damping property andmachinability, etc. However，poor corrosion resistance and wearability are actually themain obstacles to the application of magnesium alloys in practical environments. Thus，itis of great significance to make great efforts to increase the corrosion resistance of themagnesium alloys. As a kind of excellent surface treatment technology，electroless nickelplating on magnesium alloys gains not only better corrosion resistance and abrasionresistance but also uniform coating on complicated castings，which has been gained widerecognition and application in recent years.This article mainly focused on electroless plating on AZ31B magnesium alloy.Electroless Ni-P plating obtained successly on AZ31B magnesium alloy is smooth andbright, and has a high adhesion strength and good corrosion resistance. In the experiment，pretreatment process before electroless has been optimized.，and the effects of somefactors including main salt, reducing agent, complexing agent，accelerateing agent，pHand temperature to electroless and coating properties are studied. In the later experiment，the hot treatment process is also studied. The deposit coating morphology, microstructure,composition and crystallization temperature are determained and analysed by using SEMobservation and EDS analysis, XRD analysis, DSC analysis. Finally, the properties ofelectroless plating has been studied by salt spray exposure and electrokinetic potentialpolarization curve research techniques.Using acetate nickel solution as the main salt，the hardness of electroless Ni-P platingis about six times as the bare alloy.，after the process of the heat treatment，the hardness isabout1000HV. The electroless Ni-P plating has high corrosion resistance in the5%sodium chloride solution. The corrosion potential of electroless Ni-P plating shifts about0.8V to the positive potential direction than the corrosion potential of the bare alloy, andno peeling occurs on surface of the plated sample until120hours lasted. It shows that thecorrosion resistance of the plated sample improvs a lot. After the crystallization at annealing condition, the hardness of electroless Ni-P plating further improves, but thecorrosion resistance drops with the plated sample before the crystallization.