Research Of Electroless Nickel Plating On Magnesium Alloy

Magnesium alloy have a broad application prospects in the fields of automobile,electronics, aerospace and defense, etc because of its high specific strength andspecific stiffness, and advantages of favourable thermal conductivity and electricconductivity, damping vibration reduction, electromagnetic shielding, easy moldingand processing for recycling. But corrosion resistance and wear resistance ofmagnesium alloy is very poor, because it can be easily oxidate for its high chemicalactivity and formed loose porous oxidation film whose ability of protection formagnesium alloy is weak. We can resolved the problem of weak corrosion resistanceand wear resistance for magnesium alloy by means of conducting certain physical andchemical processing on the face of magnesium alloy. chemical nickel-plating usedwidely in many fields has the advantages of uniform coating thickness,excellentadhesion， low porosity compared to other magnesium alloy surface treatmenttechnology.But the existing of magnesium alloy chemical nickel-plating technologywere almost chemical nickel-plating after preplating in the middle，have weakness ofprocess trival and go against use of industry. So this paper explored the process ofmagnesium alloy chemical nickel plating directly, provided the research direction formagnesium alloy direct electroless nickel plating.In this paper, steps of pickling, activation among pretreatment process have beenanalysed. chemical nickel plating process directly of magnesium alloy and chemicalplating solution which used nickel sulfate as main salt and sodium hypophosphite asreductant was determined finally through orthogonal experiment. surface morphologyand surface microstructure of the coating were observed.By Metallographic Microscope and Scanning Electron Microscopy (SEM) andfound that surface of coating is formed by the compact ball and extrusion arrangement.Deposition rate of chemical nickel-plating was examined by weight-loss method andeffect of the lord salt, reducing agent, complexing agent, temperature, pH ondeposition rate was researched by orthogonal experiment. Phosphorus content andstructure of coating were determined by EDS(Energy Disperse Spectroscopy) and X-ray diffraction, phosphorus content was11%and wave shape of X-ray diffractionwas wide type peak.So Ni-p coating was amorphous structure.Hole sealing processing for coating was conducted and corrosion resistanceperformance was judged by salt spray test for72hours, and found that corrosionresistance performance of coating after the hole sealing was improved. The firstcorrosion point of coating appeared after ten hours, and resistance of salt fogperformance was up to6levels finally.Chemical coating was obtained after heat preservation at the temperature of220℃、350℃、450℃and found that the crystal structure of coating, corrosionresistance, hardness had changed and heat treatment can change the nature of thecoating.