Zinc Electrowinning Preparation And Properties Of New Lead-based Alloy Anodes

Lead alloys containing 0.8～1% silver is widely used as insoluble anodes in zinc electrolysis industry. However, as silver is a very expensive element, scientists made a lot of efforts to look for other alloy elements to supplement the miss of Ag in the lead alloys while not harm its comprehensive performances. Such alloy elements like Ca,Sr,RE were investigated and proved to be effective when alloyed with lead. Given some of the excellent properties of the immiscible alloy, comprehensive performance including mechanical, corrosion resistance and electrochemical properties of lead alloys by adding Al-Ti-B to the Pb-Ag alloy were investigated, according to our knowledge, no report was found in this area.By analyzing the Pb-Al Phase diagram, the thermodynamics and kinetics conditions for obtaining uniform distributed Al in Pb substrates were discussed. By applying the galvanic casting method, fistly, Pb-Ag, Pb-Ca, Pb-RE masteralloy were prepared, then, several kinds of lead alloys:Pb-1%Ag, Pb-0.15%Ag-0.11%Al, Pb-0.15%Ag, Pb-0.11%Al, Pb-0.3%Ag-0.06%Ca-0.05%Ce were obtained by remelting the masteralloy with pure lead.Through metallographic study, it was find that the grain size of the lead was decreased by alloying Al-Ti-B, Al was observed as second-phase distributed in the lead alloys substrate unevenly.By study the mechanical properties like Brinell hardness, tensile strength and elongations of these lead alloys, it was concluded that the introduce of Al-Ti-B improved the mechanical properties of the alloy.Corrosion velocity of these alloys:(Pb-0.15%Ag-0.11%Al, Pb-0.15%Ag, Pb-1%Ag, Pb-0.3%Ag-0.06%Ca-0.05%Ce)were investigated in both ZnSO4-H2SO4 and ZnSO4-MnSO4-H2SO4 system, the result show that Pb-0.15%Ag-0.11%Al was more resistant to Pb-0.15%Ag, but inferior to that of Pb-1%Ag and Pb-0.3%Ag-0.06%Ca-0.05%Ce.Stable polarization curves shows that the fresh Pb-0.15%Ag-0.11%Al alloy in system has the lowest anodic polarization overpotential, which means the best catalytic activity. EIS results convey that aluminum helps to improve the catalytic activity of lead alloys, especially after polarization for 24h.