Performance study of trace Ca elements modified Al-Mn-Ca alloy cathodes for zinc electrowinning

In this paper, the modified Al-Mn-xCa ( x = 0.02 wt.%, 0.04 wt.%, 0.06 wt.%) ternary alloy cathodes with trace Ca contents were prepared. Electrochemical tests were performed in two electrolytes (pure ZnSO 4 and high chloride (1 g/L Cl − ) ZnSO 4 solution), and the effects of elemental Ca on the properties of the ternary alloy were analyzed in comparison with 1070-Al. The simulated Zn electrowinning experiments and constant potential step timing current methods were used to obtain the economic data and to probe the initial nucleation process of Zn. When x = 0.04%, the distribution of the precipitated phase of the Al-Mn-0.04%Ca alloy is uniform and continuous, and it acts as a second-phase solid solution strengthening for the grain boundaries. The tensile strength (192 MPa) was increased by 47.7% compared to 1070-Al while maintaining a relatively high elongation. The corrosion rate in 150 g/L H 2 SO 4 (+ 1 g/L Cl − ) solution is 17.37% and 18.85% lower than that of 1070-Al; the uniformly distributed precipitated phase effectively inhibits the corrosion expansion. In addition, the nucleation process of Zn on the Al-0.9Mn-0.04%Ca electrode surface is consistent with three-dimensional continuous nucleation, while the nucleation on the 1070-Al surface is transient. This study is of practical significance for the development of highly corrosion-resistant Al-based cathode plates applicable to the complex electrolyte environment of zinc electrowinning.