Study On The Process Of Electrodepositing Aluminum On AZ91D Magnesium Alloy In Ionic Liquid

As the lightest engineering metal,magnesium alloy is widely used in various fields,but the poor corrosion resistance limit its application.To enhance the corrosion resistance,electrodeposition of aluminum plating on the magnesium alloy substrate is a useful way.In this paper,BMIC-Al Cl₃ ionic liquid was used as the electrolyte to prepare aluminum coating on the surface of magnesium alloy.The effects of different pretreatment processes,process parameters of electrodeposited aluminum plating,and electron irradiation on Al plating were investigated.Also,the feasibility of electrodeposition of Al plating on a complex part in spacecraft was demonstrated in this paper.The effects of different pretreatment processes on the corrosion resistance and microscopic morphology of the electrodeposited Al coatings on magnesium alloys were investigated.The experimental results showed that the primary and secondary zinc dip treatments of different times have limited improvement on the erosion resistance of aluminum plating,while the anodic dissolution pretreatment can fully improve the corrosion resistance of magnesium alloy after aluminum plating.The aluminum plating prepared after anodic dissolution with high current density of 15m A/cm² has fine particles and uniform plating,at which time the self-corrosion current density is 2.436×10^-5 A·cm^-2 and the self-corrosion potential is-1.494 V.To investigate the optimal parameters under different modes of current mode,it is known from the experimental results that:the optimal process parameters under Dc electrodeposition are 10 m A/cm²,35℃,60 min;the optimal process parameters under pulsed electrodeposition mode are 15 m A/cm²,25℃,90 min.Test whether the prepared aluminum plating can be applied in space environment.Firstly,the solar absorption ratio of the aluminum plating prepared by the three different processes was calculated,in which the solar absorption ratio value of the plating prepared by pulsed aluminum plating after anodic dissolution was 15.98%,with good optical properties.The plating was then subjected to different doses of electron irradiation.Through the analysis of microscopic morphology,surface elements,and crystal structure,it can be known that when the dose of electron irradiation exceeds 1×10¹⁶cm²,the coating will produce certain damage.The mechanical properties of the plating were tested and found that the bond strength of the plating was not significantly affected by the electron irradiation,but the microhardness was slightly reduced.The article concludes with the electrodeposition of the complex magnesium alloy parts,using the hieroglyphic anode method,which covered the surface of the complex parts with a flat and uniform aluminum layer.The performance of the electrodeposited Al layer was then characterized.The surface thickness of the layer averaged about 10μm,with uniformity of-1.35～+1.35μm,and bond strength of about 20 MPa,which can meet the needs of engineering applications.