Research On The Corrosion Resistance And Zinc Nucleation Mechanism Of Aluminum Alloy Cathodes For Zinc Electrowinning

The content of fluorine and chloride ions in the electrolyte of electrowinning zinc is extremely high,which lead to the seriously corrosion and consumption of currently employed aluminum cathodes,resulting in the increase of the cost.It is an urgent mission to develop cathode materials with strong mechanical property,good corrosion resistance and good electrochemical properties.Meanwhile,the study on the deposition mechanism of zinc on the surface of Al cathode is beneficial to the design of cathode materials.In this paper,waste 1070 pure aluminum cathodes for industrial applications are selected as raw materials.And Mn,RE and Zn elements are added for melting casting and rolling to prepare aluminum alloy cathodes respectively.The main contents of the study are as follows:(1)The hydrogen evolution and cathodic reaction kinetics on aluminum alloy cathodes are discussed through electrochemical measrements.(2)The microstructure of the prepared alloy is analyzed,and the discussion of the parameters such as the corrosion potential,corrosion current,and electrochemical corrosion rate of the aluminum alloy is conducted in the electrolyte of wet zinc smelting.Besides,the influence of alloy elements on corrosion resistance is explored combined with the immersion corrosion tests.(3)The initial nucleation mechanism of the zinc deposition on the alloy surface is investigated via scanning electron microscopy and chronoamperometry.(4)Pilot study on simulated zinc electrowinning,and compared with related technical indicators of 1070 pure aluminum cathode.The conclusions from the above research are presented in the following.(1)The addition of Mn,RE and Zn elements in the alloy exhibits a positive effect on the hydrogen evolution and zinc deposition reaction.The electrocatalytic activity of the Al alloy is slightly improved,which is beneficial to the zinc deposition reaction.Meanwhile,the deposition potential of zinc on Al alloys is lower than 1070 pure aluminum cathode,which is conducive to the reduction of energy consumption.(2)The addition of Mn?RE and Zn elements in the alloy can refine the grain structure and reduce the grain size.(3)The corrosion resistance of the alloy has been improved to varying degrees.Al-0.3%RE presents the best corrosion resistance,followed by Al-0.6%Mn cathode.(4)The zinc nucleation on the cathode surface reveals that the zinc nucleation on 1070 pure aluminum and Al-0.6%Mn cathodes follows the three-dimensional transient nucleation mechanism.Whereas,Al-0.5%RE,Al-0.6%Mn-0.5%RE and Al-0.6%Mn-0.25%Zn cathodes follows three-dimensional continuous nucleation mechanism.(5)The pilot tests indicate that the current efficiency of Al-0.6%Mn cathode reaches 94.22%,which is higher than that of 1070 pure aluminum.The current efficiency of the other alloys keeps around about 90%.In summary,Al-0.6%Mn,Al-0.5%RE,and Al-0.6%Mn-0.5%RE exhibit good comprehensive performances.Especially,the indicators on Al-0.6%Mn cathode are better than the current employed pure aluminum cathode in industrial application,which is expected to achieve industrial application in the future.