| In this experiment,tin coating was successfully prepared on the surface of aluminum substrate with copper-tin alloy as intermediate layer by electrodeposition technology,and the morphology and properties of copper-tin alloy coating and tin coating under different current density were analyzed.Scanning electron microscope(SEM),hardness tester,micro-nano mechanics comprehensive test system,energy spectrometer,laser confocal,X-ray diffraction(XRD),electrochemical workstation and salt spray test box were used to characterize the surface morphology and phase composition of copper-tin alloy coating and tin coating,and the physical properties and corrosion resistance of the coating were tested.The study on the properties of copper-tin alloy coating under different current density shows that when the current density is 0.6 A/dm2,the hardness of the coating is 230 HV and the friction coefficient is 0.129.The coating has excellent hardness and good wear resistance.Copper and tin elements in the coating can improve the hardness and wear resistance of the coating.The corrosion current density of the coating at 0.7 A/dm2is0.624×10-6A/cm2,which is lower than that of the coating under other conditions.The tin element in the coating is beneficial to improve the corrosion resistance,and the increase of coating thickness promotes the hardness,wear resistance and corrosion resistance of the coating.The study on the properties of tin coating under different current density shows that under the process condition of electrodeposition tin current density,the hardness of tin coating in 0.2 A/cm2is 61 HV,the friction coefficient is 0.28,and the polarization potential is-0.982 V.Compared with other coatings in the current density range,the coating not only has better hardness performance,but also has better friction resistance.In addition,the coating also has excellent corrosion resistance.With the increase of current density,the number of bubbles wrapped in tin coating increases.The coating shows better performance at low current density.Taking the current density of electrodepositing copper-tin alloy as the process condition.When the current density is 0.7 A/dm2,the hardness is 119 HV,and when the current density is 0.8 A/dm2,the friction coefficient of tin coating is 0.227,both of which are the best values in the experimental range.The hardness and wear resistance of tin coating are related to the element change of copper-tin alloy coating,the hardness change of tin coating is proportional to the proportion of copper in the copper-tin intermediate layer,while the proportion of tin in the copper-tin interlayer increases reduces the whisker production on the surface of the copper-tin coating,which leads to the improvement of the surface smoothness of the tin coating and makes the tin coating have better wear resistance.Increasing the thickness of the coating can improve the resistance of the coating in corrosion environment.In this paper,through experimental study,the performance of copper-tin alloy coating and tin coating under different current density is analyzed,and the optimum process parameters of electrodepositing copper-tin alloy coating and tin coating on aluminum alloy surface are obtained through experimental study. |
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