Characteristics of Pb-based alloy prepared by powder rolling method as an insoluble anode for zinc electrowinning

摘要

In this study, a Pb- Ag alloy anode was prepared by a "powder rolling method", and its possible use as an alternative insoluble anode for an electrowinning application was investigated. The Pb-0.71 wt.% Ag cast-rolled alloy, which is currently an insoluble anode for zinc electrowinning, caused remarkable creep deformation under the stress of 15.0 MPa in a 150 g L-1 H_2SO_4 solution at 303 K, and fractured at about 100 ks. The Norton plot data allowed the determination that the creep of the Pb-0.71 wt.% Ag cast-rolled alloy proceeded by a "dislocation mechanism". On the other hand, a Pb-0.71 wt% Ag powder-rolled alloy did not deform at all even at a current density of 10 mA cm~(-2), which confirmed the fact that the Pb-0.71 wt.% Ag powder-rolled alloy was an outstanding creep-resistant material in a highly concentrated H_2SO_4 solution. For galvanostatic electrolysis, it was shown that the oxygen evolution overpotential and the energy efficiency of the Pb-0.71 wt.% Ag powder-rolled alloy were nearly equal to those of the present Pb-0.71 wt.% Ag cast-rolled alloy. Moreover, the amount of Pb impurities in the deposited Zn on the Al cathode was a low value, i.e., only 57% of the Pb-0.71 wt.% Ag cast-rolled alloy. Therefore, the Pb-0.71 wt.% Ag powder-rolled alltiy may be considered an alternative Pb-based insoluble anode with both an excellent durability and a good energy efficiency for electrolysis.