| At present, the Pb-(0.6-0.8)%Ag and Pb-(0.2-0.3)%Ag-(0.06-0.1)%Ca alloy are the main anode materials in hydrometallurgical extraction of zinc at home.At abroad, commercial anode also include Pb-(0.2-0.6)%Ag-(0.06-0.1)%Ca-0.2%Zr alloy.The advantage position of lead alloy anode still can't completely be replaced, due to its excellent corrosion resistance in high concentration H2SO4 system. There are some difficulties in their use, one is lead corrosion products in the deposit at the cathode which decrease the purity.Secondly the oxygen overpotential is relatively high to increase the cell voltage and decrease energy efficiency. Thirdly the short circuit phenomenon occur easily due to the poor mechanical performance of lead alloy.Owing to these problems there is always interest in finding methods to improve anode mechanical properties and minimize the corrosion and overpotential problems. In this paper, the metal aluminium is used as the body, surface treatment of the metal aluminium is needed, then on which Pb-Ag alloy is casted, get the new aluminum body Pb-Ag alloy composite anode material finally in order to improve the mechanical properties of aluminum matrix and Pb-Ag alloy, aluminum body is conducted by surface treatment. The new aluminum body Pb-Ag alloy composite anode material possess broad application prospects because of its strong mechanical properties, lower production cost and energy consumption, the well performance in zinc electrolytic experiment.In this paper, we get Pb-0.3%Ag and Pb-0.5%Ag alloy by gravity casting method under certain conditions.And then,aluminum matrixs are processed by anodic oxidation and Sn plating respectively. Finally, we get Al/Pb-0.3%Ag and Al/Pb-0.5%Ag alloy composite anode material by casting Pb-Ag alloy on aluminum matrixs.Through the metallographic analysis of lead alloy, we find that the lead grain is thinner with Ag additions, and Ag was distribute in the lead by the second phase particle with the serious segregation.Also the vickers hardness of lead alloys are studied.The results show that the hardness of the lead has improve with Ag, the casting alloy hardness of Pb-0.5%Ag is 1.82kg/mm2 higher than that of Pb-0.3%Ag; the Al/Pb-0.5%Ag rolling alloy is 3.66kg/mm2 higher than Pb-0.5%Ag casting alloy; explaining rolling can improve the alloy hardness.Through the cross section analysis of composite anode material, we find that the binding force between Pb-Ag alloy and aluminum matrix after anodic oxidation is best.There is no obvious hole,crack and crackle on the border.The diffusion of oxygen atoms is intense in the alloy interface.While for aluminum matrix after Sn plating, the binding force is not so good, there is obvious hole,crack and crackle on the border. The union between grain is loose.The corrosion rates of Pb-0.3%Ag and Pb-0.5%Ag alloy anode sample through the different treatment in H2SO4 system are studied. The anode oxidation film morphology and physical phase composition of Pb-0.3%Ag alloy through the different treatment which after 8 hours polarization in H2SO4 system is analysised too. The results show that the anode corrosion rate increase along with the increase of the current density.The corrosion rule is the same, regardless of Pb-0.3%Ag alloy and Pb-0.5%Ag alloy in H2SO4 system.The anode corrosion rate of Al/Pb-0.5%Ag(anodic oxidation embossed) is the lowest,followed closely by that of anode Al/Pb-0.5%Ag(Sn plating embossed). Anodic oxidation film of Pb-0.3%Ag embossed alloy is loose and porous. Anodic oxidation film of Al/Pb-0.3%Ag(Sn plating embossed) and Al/Pb-0.3%Ag(anodic oxidation embossed) are compact with the structure of large particles and loose debris stacking.EDS analysis shows that the three kinds of anodic oxidation film are made up of the more Pb,O and the less S. XRD results showed that the composition of three anodic oxidation film is almost the same.It is oxide and sulfur of lead. Anodic oxidation film of Al/Pb-0.3%Ag(anodic oxidation embossed) possesses complex components.The dynamic parameters of the anode sample are tested through the polarization curve,tafel curve,circulation current-voltage curve,electrochemical impedance spectrum in the acidic zinc sulfat electrolyte system. The anode polarization potential of Al/Pb-0.5%Ag(anodic oxidation embossed) is the lowest and the catalytic activity is the best through the anode polarization curve.The Al/Pb-0.5%Ag(anodic oxidation embossed) possess the the biggest corrosion potential the lowest corrosion current density and the best corrosion resistance through tafel curve.The Al/Pb-0.5%Ag(anodic oxidation embossed) has a positive effect for PbSO4â†'PbO2 and corrosion resistance through circulation current-voltage curve. The Al/Pb-0.3%Ag and Al/Pb-0.5%Ag (anodic oxidation embossed) possess the less curvature radius and the higher catalytic activity.The Al/Pb-0.5%Ag (anodic oxidation embossed) possess the least curvature radius and the highest catalytic activity. Generally the catalytic activity of embossed alloy is higher than that of unembossed At last, the main technical and economic indexes of the new aluminum body Pb-Ag alloy composite anode material are tested in the process of zinc electrolysis. The results show that the new composite anode is better than Pb-Ag anode in the slot voltage, current efficiency and so on. |
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