Study On Surface Coating And Electrochemical Performance Of Aluminum-based Lead Alloy Composite Anode

The Al/Pb-Ag alloy composite anode has high mechanical strength and excellent electrochemical performance,and the fence type composite anode plate processed into a leading position in the zinc electrowinning industrial application.In industrial production,in order to maximize the life of the anode and improve the electrocatalytic activity of the anode material.Usually,before the anode material is used in the tank,proper surface pretreatment of the anode material is required to improve the performance of the anode.In this paper,the effects of anode surface pretreatment on the anode material and the changes in zinc yield and cell voltage after 15 days of continuous electrolysis of different anode plates were investigated.In this paper,the electrochemical method,the phase morphology detection method and the data under industrial production conditions are studied,and the following conclusions are obtained:(1)The surface of the Al/Pb-Ag alloy anode was pretreated without F and F-doped two different sulfuric acid solution systems by anodizing.The results show that the surface of the F-doped film layer is continuous and dense.At the same time,it has a high surface roughness,and the thickness of the entire film reaches an average of 35?m.Electrochemical tests show that the composite anode after F-doped exhibits excellent electrochemical performance.The anode surface film layer which is F-undoped has a large number of defects and many voids,and the film layer thickness is only 3.75?m,and the electrochemical performance is not as good as the former.Compared with the film formation mechanism in two different plating solutions,it is found that fluoride ions play an important role in the pretreatment of the anode surface.The resulting transition layer PbF₂ isolates the direct contact between PbO₂ and Pb,which promotes the formation of?-PbO₂ with excellent electrocatalytic activity in the film layer.It inhibits the excessive oxygen evolution behavior of the anode surface during the film formation process.(2)During the surface pretreatment of lead alloy anode,the current density has a great influence on the growth and electrochemical properties of the surface layer.With the increase of filming current density,the apparent exchange current density of the anode mainly increases first and then decreases.Under the condition of 5A/dm²,the diffraction peak of?-PbO₂in the oxide film formed on the anode surface is the strongest,and the electrochemical properties is excellent.However,the surface of the anode formed at a low current density is porous,the surface active oxide?-PbO₂coverage is not high,and the electrocatalytic activity is poor;Fluoride ion concentration is also a crucial factor for film formation on the anode surface.Compared with film formation under low fluorine concentration,the film layer obtained by high concentration of fluoride ions is not dense enough and has many defects,and the electrochemical performance is not ideal.After film formation by low-silver and high-silver lead alloys,it was found that the surface of the lead alloys was basically covered by the ceramic layer?-PbO₂with electrocatalytic activity,and both of them were excellent in the electrowinning zinc experiment.The low-silver film-forming anode has better oxygen evolution activity than the uncoated high-silver lead alloy,indicating that the actual catalytic effect is the oxide film layer on the surface of the lead alloy.(3)Surface pretreatment of the fence-type Al/Pb-Ag alloy narrow plate anode and wide plate anode for zinc electrowinning industry based on superior film formation conditions.The cell voltage of the conventional lead alloy anode plate,the zinc yield,the zinc grade,and the anode mud analysis produced at the same time node were compared by continuous electrolysis for 15 days.The results show that in the complex case of the actual production of Zinc,different anode plates will have a greater impact on the tank voltage,zinc production and anode mud production.The fence-type Al/Pb-Ag alloy narrow-plate anode has higher current efficiency and better zinc quality,and the cell voltage is relatively lower.After 15 days of electrolysis,the anode mud produced by the narrow-plate anode contains a large amount of?-PbO₂ with corrosion resistance and electrocatalytic activity and more MnO₂ with electrocatalytically active.