Preparation Of Aluminum And Aluminum-magnesium Alloys By Pulse Electrodeposition

Aluminum and aluminum-magnesium alloys became perfect protective material because of its good corrosion resistance,decorative,antioxidant and mechanical property.Due to light quality,high theoretical hydrogen storage capacity,aluminum-magnesium alloys have widely application future as hydrogen storage material.Electrodeposition was one of effective methods of preparation ultrafine and high purity.Aluminum and aluminum-magnesium alloys prepared by electrodeposition in nonaqueous solution.The basis of preparation coating was deposition system.The key of preparation coating was deposition method.The composition and microstructure was controlled by parameter to forming ultrafine and high purity alloys.AlCl₃-LiAlH₄ organic solvent system is first applied to the system of electrolytic aluminum.It can be used at room temperature,not only save energy effectively,also does not affect the mechanical properties of matrix.In this paper,on the basis of domestic and foreign research,aluminum and aluminum-magnesium alloys are prepared by direct current or pulse electrodeposition in the AlCl₃-LiAlH₄-benzene-THF organic solvent system.Electrochemistry experiment are conducted by using three-electrodes system.Electrical conductivity of the electrolyte of aluminum-magnesium alloy are measured by ac impedance?EIS?.Corrosion resistance of aluminum and aluminum-magnesium alloys coating are studied by ac impedance method and Tafel polarization curve.The surface morphology,composition and content of aluminum and aluminum-magnesium alloys were analyzed by using scanning electron microscope?SEM?,energy spectrum?EDS?and X-ray diffraction?XRD?.Current density,pulse duration ratio,frequency,adding magnesium ions method and experimental environment have influence on crystal structure of coating.Results show that high purity aluminum coating are prepared by pulse electrodeposition.Content of aluminum are high as 99.43 wt %.There are a great influence on aluminum coating through changing parameters,such as duration ratio,current density,etc.The smaller the duration ratio,the smaller grain size of coating.The smallest grain size up to 0.5mm.Grain sizes increases with increase of current density in acertain range.The grain sizes can be refined by adding a small amount of MgCl₂.Magnesium bar are used as the anode,and MgCl₂ are added to electrolyte when direct current deposit.The main composition of aluminium-magnesium alloys are Al₃Mg₂ and Al₁2Mg₁7,it can be seen through XRD spectrum diagram.Magnesium content of coating is 4.61 wt % when the current density of 0.3 A/cm2.The greater the current density,the higher the magnesium content of coating in a certain range.Increase the number of magnesium bar,magnesium content are increased.but the trend of growth is not obvious.magnesium content are 7.56 wt % when five magnesium bar.Increase current density,grain sizes and magnesium content are creased for pulse electrodeposition.When the current density of 20 mA/cm2,grain sizes up to 30-50 m m,magnesium content are 3.17 wt %.The greater duration ratio,the greater the grain sizes and magnesium content in the coating.The minimum grain sizes up to 5m m when the duration ratio is 0.02:0.08.Corrosion resistance experiment of aluminum and aluminum-magnesium alloys are conducted by ac impedance and polarization curve.Studied corrosion resistance of aluminum.we found that the greater the duration ratio,the better corrosion resistance.In other words,the grain sizes are larger,the better corrosion resistance.The impedance is the largest when the magnesium content is 2.54%?mass fraction?for corrosion resistance experiment of aluminum-magnesium alloy coating.The higher the magnesium content,the greater the corrosion resistance of coating.