On the way to develop co-containing lead anodes for zinc electrowinning

In this work, the effect of cobalt on the properties and performance of lead anodes for zinc electrowinning is investigated. An attempt was made to produce Pb–Co mixture anodes by mechanical alloying. It is observed that milling is not capable of producing a solid solution, even by adding stearic acid as a process controlling agent, as all powders stuck to the balls or cold welded together. Moreover, plasma spraying method was used to apply Co-containing lead layers on the surface of the pure Pb sheets followed by rolling in order to smooth the surface. Both as sprayed and sprayed and rolled samples with 1, 3 and 5 wt.% Co concentrations were evaluated in terms of corrosion properties and oxygen evolution potential. The analysis of the microstructures and voltammograms confirm the best corrosion resistance for 3 wt.% Co containing, sprayed-rolled samples compared to none treated lead sheet. Microstructure investigations revealed that the spherical Co particles were distributed on and within the sprayed layers. Potentiostatic measurements of the rolled samples show that the addition of Co up to an optimum amount of 3 wt.% decreases the oxygen evolution potential from 1.64 to 1.55 V; and the starting current values decreases noticeably from 3.1 × 10− 4 to 5.5 × 10− 5 A, respectively. Moreover, the effect of the amount of area reduction on the anodic properties of the rolled samples was investigated. The microstructure of anodic layer was also studied using SEM.

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► Mechanical alloying is not capable way for producing uniform Pb–Co alloy.
► Co up to an optimum between 1 and 3 wt.% decreases the oxygen evolution potential.
► Co up to an optimum between 1 and 3 wt.% decreases the current of oxygen evolution.
► The area reduction of sprayed samples has important effect on the anodic properties.
► Different analyses confirm the best corrosion resistance of sprayed-rolled samples.