The Research On Additives In Solution Of Electroless Plating Ni On Magnesium Alloy

Magnesium and its alloys are the lightest nonferrous structural metals and have apromising application prospect in aeronautic industry, automotive and electronicindustry and so on. But the corrosion potential of magnesium alloys is extremely low,greatly limited the application of magnesium alloys. Corrosion resistance of magnesiumalloy surface can be improved by electrolss nickel plating, However, magnesium alloysare corrode easily in electroless plating solution because of their high chemical andelectrochemical activity. It will directly influence the performance of electrolss nickelplating. This article electroless nickel plating coating of good adhesion on magnesiumalloy can be obtained by the methods of introducing inhibitor additives, selecting thesuitable stabilizers, changing the type of nickel source in the plating solution. Theperformance of the coatings are characterized by using SEM, EDS, XRD,electrochemical method and so on.By using electroehemical polarization curves, full-immersion weight-lossexperiment to study the corrosion behavior of different inhibitors on the magnesiumsubstrate. By doing the selecting work this article gets four inhibitors with excellentinhibition efficiency for AZ91D magnesium alloy:1%methenamine—42.20%,0.1%sodium nitrite—77.19%,2%ammonium fluoride—76.59%,2%ammoniumbifluoride—86.70%. The already selected four inhibitors are compounded with organic-inorganic and inorganic-inorganic. The influences of Species and composition ofcompound inhibitors on the corrosion rates and inhibition efficiency for AZ91Dmagnesium alloys in solution are studied. The result finds inhibitor compounds show avery good synergistic effect. The compounds have improved the protecting effect formagnesium alloy, show a higher inhibition efficiency than any of the used compoundinhibitors. The best inhibition efficiency of every compounds with ratios is defined asfollowing: with1%methenamine+2%ammonium bifluoride—90.09%, with1%ammonium fluoride+1.5%ammonium bifluoride—95.04%, with0.1%sodium nitrite+2%ammonium bifluoride—92.88%. The effects of single and compound inhibitor to plating rate and performance ofcoating are studied. The every compounds with ratios of the best inhibition efficiency isdefined by1%ammonium fluoride+1.5%ammonium bifluoride, as the inhibitors inelectroless plating process of nickel sulfate system.The influences of four stabilizers on stability, plating rate, surface morphology andthe porosity of coating are studied.The best effect of stabilizer with10mg/LKI isdefined as the stabilizer in electroless plating process of nickel sulfate system. The bestformula of electroless plating process using nickel sulfate as main salt is defined bysingle factor experiment and orthogonal experiment. The Ni-P coating obtained by theoptimum process is very meticulous, uniform and good adhesion. The beginninggrowth procedure of electrolss nickel plating is preliminary explored.The best formula of electroless plating process using nickel hydroxide as main saltis defined by single factor experiment and orthogonal experiment. The coating of goodadhesion on the magnesium substrate can be obtained in electroless plating solutionafter simple preparation.