Preparation And Performance Study Of Aluminum-based Multi-element Alloy Cathode For Electrowinning Zinc

In recent years,with the declining quality of mineral products,the increase of impurity content in electrolyte,the wet zinc smelting industry faces severe challenges.The corrosion of aluminum cathode during zinc deposition is intensified,the service life is shortened,the zinc stripping is difficult,and other problems directly affect the normal production of electrowinning zinc.Therefore,research and development of cathode electrode materials with high strength,strong corrosion resistance and excellent electrochemical performance have become a reality.This paper is based on pure aluminum cathode to research.In which,with adding the enhanced elements Mn,Mg,Cr and RE respectively for casting.The microstructure of the prepared alloy was observed under an optical microscope,and the effect of the added elements on the microstructure of the alloy and the distribution of the crystal grains were investigated.By using cathodic polarization curves to study electrochemical behavior of electrodes after adding alloying elements.Simultaneously,the kinetics of hydrogen evolution of alloy electrodes is analyzed and discussed by Tafel linear fitting.The corrosion potential and corrosion current parameters of the alloy electrode were obtained by means of Tafel curve.At the same time,the corrosion dissolution rate and surface corrosion microcosmic morphology measured by the corrosion weight loss immersion experiment were combined to study the effect of additive elements on the corrosion resistance of the electrode.The main findings are as follows:?1?The microstructure of the aluminum matrix is refined and the grain size is reduced after adding the alloying elements.From the degree of refinement,Mg and RE elements have the largest degree of refinement of aluminum matrix grains,followed by Cr,and finally Mn.Meanwhile,with the increase of alloying element addition the refinement degree of grain microstructure increases.?2?Alloying elements increases the response rate of the electrode,promotes the negative shift of the electrode response potential,and improves electrocatalytic activity.In the prepared Al-Me binary alloy,the optimum element contents were1.5%Mn,2.0%Mg,and 1.0%RE,respectively.The kinetic process of hydrogen evolution is shown in 500·Am^-2,The magnitude of hydrogen evolution overpotential is:Al-2.0%Mg>Al-0.2%Cr>Al-1.0%RE>Al-1.5%Mn>Pure Al.The apparent exchange current density increases at least 10 order of magnitude,and the electrode reaction rate is increased when hydrogen evolution overpotential equals 0V.The i₀ of optimal alloy group is:Al-2.0%Mg>Al-1.0%RE>Al-1.5%Mn>Al-0.2%Cr>Pure Al.?3?The type and amount of alloying elements have a significant influence on the corrosion resistance of the electrode.The corrosion resistance of the Mn-containing electrode is enhanced.Addition of Cr element will aggravate the dissolution of the aluminum matrix,and the corrosion resistance of the Mg and RE alloy electrodes will vary with the addition amount.Among them,the corrosion resistance of the better group was:Al-1.5%Mn>Al-1.0%RE>Al-2.0%Mg>Pure Al.?4?The performance of aluminum-based ternary alloys Al-1.5%Mn-Me shows that the electrode response rate is the same as that of Al-Me binary alloys.The response potential at the same current is negatively shifted,the polarization degree is increased,and the inhibition of hydrogen evolution is hindered.The best performance in the same alloy group was 1.0%Mg,1.0%RE and 0.2%Cr,respectively.Their overpotential magnitudes at 500·Am^-22 current density are Al-1.5%Mn-0.2%Cr>Al-1.5%Mn-1.0%RE>Al-1.5%Mn-1.0%Mg>Al-1.5%Mn>Pure Al.The order of apparent exchange current density at zero potential is as follows:Al-1.5%Mn-1.0%Mg>Al-1.5%Mn-1.0%RE>Al-1.5%Mn-0.2%Cr>Al-1.5.?5?Adding Mg,Cr,and RE on the basis of Al-1.5%Mn,the corrosion resistance of the electrode is significantly higher than that of pure aluminum on the binary basis,and the corrosion resistance is enhanced.The addition of Mn and Cr reduces the defects caused by Cr and improves corrosion resistance.The corrosion resistance of the superior group is as follows:Al-1.5%Mn>Al-1.5%Mn-1.0%Mg>Al-1.5%Mn-1.0%RE>Al-1.5%Mn-0.5%Cr>Pure Al.?6?The comprehensive properties of Al-1.5%Mn-1.0%Mg,Al-1.5%Mn-1.0%RE,Al-1.5%Mn-0.5%Cr,Al-1.5%Mn,Al-1.0%RE,and Al-2.0%Mg Better,can be further experimental research as a zinc electrowinning application practice.