Anodes for Electrowinning

Anodes used in the electrowinning of base metals, such as copper and zinc, are almost exclusively lead alloys. The copper industry uses lead-calcium-tin. While, zinc utilizes lead-silver. In copper, lead-calcium-tin is favored to avoid the cost of the silver addition. Stabilization (minimize corrosion) of the Pb-Ca-Sn anodes is maintained by the careful control of cobalt in the electrowinning electrolyte. In zinc electrowinning, Pb-Ag is the norm because cobalt addition is not an operation. The electrolyte cobalt concentration must be minimized to allow for zinc deposition. The silver alloy impacts some corrosion resistance to the base lead. Lead based anodes are used because of their low cost and robustness. The major drawbacks to them are sludge generation (leading to product quality issus) and high oxygen overpotential (higher power costs).

To overcome these drawbacks new technology like the Mesh on Lead (MOL) anode offered by ELTECH Systems is being developed. The MOL anode is a composite structure combining the benefits of a standard lead anode with power savings of precious metal oxide coated titanium found typically in dimensionally stable anodes (DSA). The MOL product is still being developed to overcome its major drawback, cost.

For more information, try one of the books on DocCopper's Copper Book Page.

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