Current efficiency is a measure of the effectiveness with which electrical current supplied to an electrolytic or electrochemical process is utilized for the intended reaction, expressed as a percentage of the theoretical maximum. In the context of mining and mineral processing, current efficiency is most directly relevant to aluminium smelting operations that follow the bauxite mining and alumina refining process chain. In the Hall–Héroult electrolytic reduction cells, current efficiency measures the proportion of electrical current that contributes to the reduction of alumina to metallic aluminum, as opposed to current consumed in parasitic reactions such as the reoxidation of dissolved aluminum by CO₂ in the electrolyte bath. Typical current efficiency values in modern aluminium smelting cells range from 92% to 96%, with losses attributable to alumina concentration fluctuations, bath chemistry variations, and cell operating temperature. In gold electrowinning operations, current efficiency similarly describes how effectively current is used to deposit gold from pregnant electrolyte solutions onto cathode blanks. Improving current efficiency reduces energy consumption per tonne of metal produced, lowering operating costs and carbon intensity, which is a significant focus in the bauxite-to-aluminium value chain.
