Study On Electrochemical Performance Of Aluminum - Based Lead Silver Alloy

The Pb-(0.5wt～1.0wt%) Ag alloy was often used as the anode material in the modern zinc electrowinning industry, but the anode have some shortcoming, such as the high oxygen evolution potential, poor corrosion resistance, poor electrical conductivity and so on. However, the PbO2 has good electric-catalytic activity and get the attention of the researchers.In this paper, Al/Pb-0.3%Ag, Al/Pb-0.3%Ag film-plating, Al/Pb-0.75%Ag and Al/Pb-0.75%Ag film-plating are selected for research subjects. After 12h,24h,48h, 96h electrolysis at the current density of 10000A·m-2 in two electrolyte at 35 ℃, four kinds of anodes were investigated using cyclic voltammetry, anodic polarization test, XRD test, SEM test and the corrosion rate test after electrolysis. The results are drawn as follows:(1) 150g/L H2SO4, the temperature and the current density are 35 ℃ and 10000A/m2, respectively.The oxygen evolution potential and corrosion rate of four anodes are as follow: Al/Pb-0.75%Ag film-plating is lowest. Al/Pb-0.3%Ag film-plating is higher than Al/Pb-0.75%Ag, which is lower than Al/Pb-0.75%Ag film-plating. Al/Pb-0.3%Ag is highest. With increasing electrolysis time, the oxygen evolution potential and corrosion rate of four anodes are gradually reduced. The oxygen evolution potential and corrosion rate of Al/Pb-0.75%Ag film-plating are 1.886V(SCE) and 10.004 g·h-1m-2, respectively. And the content of silver is much more contribute to enhance the electric catalytic activity of anodes. The major phase of the anodes oxide layer consisted of α-PbO2 and β-PbO2. No matter whether the Al/Pb-0.75%Ag anode coating or not,the morphology of anode oxide layer are made of a large number of small asymmetry of grain. The oxide layer of Al/Pb-0.3%Ag film-plating inlaid tetragonal crystalline grains, and and the grain size is the largest. The oxide layer of Al/Pb-0.3%Ag inlaid with thin slice grain.(2) 150g/L H2SO4,800mg/L Cl-, the temperature and the current density are 35 ℃ and 10000A/m2, respectively.The oxygen evolution potential and corrosion rate of four anodes are as follow: Al/Pb-0.75%Ag film-plating is lowest. Al/Pb-0.75%Ag is higher than Al/Pb-0.3%Ag film-plating, which is lower than Al/Pb-0.75%Ag film-plating. Al/Pb-0.3%Ag is highest. With increasing electrolysis time, the oxygen evolution potential of four anodes are gradually reduced. The oxygen evolution potential and corrosion rate of Al/Pb-0.75%Ag film-plating are 1.6933V(SCE) and 11.575 g-h-1·m-2, respectively. Compared with high content of silver, film-plating is much more contribute to enhance the electric catalytic activity of anodes. The major phase of the anodes oxide layer consisted of α-PbO2. The morphology of Al/Pb-0.3%Ag film-plating and Al/Pb-0.75%Ag film-plating oxide layer are similar, are made by a large number of asymmetry of the grain. The compact structure and good corrosion resistance is obtained. However, the morphology of Al/Pb-0.3%Ag and Al/Pb-0.75%Ag oxide layer are similar, are studded with large regular grain. The surface of anodes oxide layer appear cavities and pitting. Furthermore, the corrosion resistance of those anodes are poor.In a word, the property of Al/Pb-0.75%Ag film-plating is best in the sulfuric acid electrolyte and chlorine ion sulfuric acid electrolyte.