The issue of current efficiency in insoluble lead anodes

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In the electrowinning section of a copper hydrometallurgical plant, the anode is an insoluble Pb-Sn-Ca alloy anode, while the cathode is a permanent stainless steel cathode; this setup is used to process copper sulfate solutions containing 45 g/l of copper, in order to produce standard cathode copper products. The electrowinning workshop uses two types of lead anodes: one is domestically produced, and the other comes from a company in South Africa; these anodes are placed in separate electrowinning cells, while the cathodes are supplied by the same company. All the electrowinning cells have the same cathode and other production parameters such as current density, circulation rate, solution composition, and temperature, except for the anode used. The problem is that the cathode copper production in electrowinning cells equipped with domestic anodes is high, with a current efficiency of around 90%; however, the anodes wear out rapidly, as layers of lead oxide film keep peeling off ； The production volume of the electrowinning cells equipped with imported South African anodes is much lower, with a current efficiency of 75–80%; however, the anodes suffer little wear, have a dense and smooth surface, and no flaking oxide layer. I would like to ask the experts what causes this? What are some ways to improve the current efficiency of cells used for depositing South African anode plates? Thank you, I’ll be waiting here, hoping to become friends with you.