| Magnesium alloys are more and more paid attention because of its good advantages andwidely used in automotive, aerospace and3C fields.But application of magnesium alloys islimited greatly due to low electrode potential,high activity and poor corrosion resistance.Sothe protection of magnesium alloys and improving corrosion resistance of magnesium alloysis of great significance to extend the application of magnesium alloys.In this paper, appropriate pretreatment process of AZ80magnesium alloy is obtainedthrough the experiment.Optimal process parameter of electroless Cu plating on AZ80magnesium alloy is acquired by orthogonal experiment. On the basis of the optimalelectroless Cu coating TiO2nanoparticles is added in the composite coating and orthogonalexperiment is the same with preparation on composite coating of nano-TiO2/Cu.The surfacemorphology,ingredient,microhardness and corrosion resistance of electroless Cu coating aswell as composite coating is analyzed by SEM,EDS,XRD,microhardness tester andelectrochemical testing system.Results show that the optimal process parameters for electroless Cu coating are45℃,pH value11.5, complexing agent20g/L,annexing agent3g/L.XRD shows that it has obviouspeak of three strong lines in the Cu coating.The electroless Cu coating is covering on thematrix fully,which showed by SEM.Fine Cu particles distribute on the surface dense anduniformly.Plating speed is roughly4μm/h.The open circuit potential of optimal Cu coatinggroup increases107mV compared with AZ80matrix.The microhardness has achieved to230HV in comparison to97.6HV of AZ80matrix and corrosion current density reduces5timesin contrast to1.58mA/cm2of AZ80matrix.The optimal process for nano-TiO2/Cu compositecoating is1.5h,10g/L TiO2,5g/L dispersant,3g/L surfactant.Ti weight ratio is0.43%in thenano-TiO2/Cu composite coating by EDS.SEM shows that composite coating is more smoothand covering much completely.However,composite coating speed is3.33μm/h.The opencircuit potential of optimal composite coating is improved180mV compared with AZ80 matrix.The microhardness is274.3HV and increased176.7HV in contrast to AZ80matrix.Corrosion current density reaches0.23mA/cm2and reduces7times in comparison toAZ80matrix.The open circuit potential,microhardness and corrosion resistance of optimalcomposite coating is higher than that of electroless Cu coating.These phenomenon declaredthat nanoparticles have reinforcement function on the mechanical properties and corrosionresistance of electroless composite coatings. |
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