The half-reactions are

The electrode potentials used here are only approximate because they are for dilute aqueous solutions, not for a fused salt. They do indicate that a large potential must be applied across the electrodes of the cell before electrolysis and decomposition of the salt will begin.

Electrolysis is the only practical process for obtaining aluminum metal from its ores, primarily Al₂0₃. Many other metals are either obtained or purified by electrolytic cells. For example, if a current is passed through two copper electrodes immersed in a copper sulfate solution, copper will be oxidized to Cu²⁺ ions at the anode, and Cu²⁺ ions will be reduced and will plate as metallic copper on the cathode. If an ingot of impure copper is used as the anode, then pure copper will build up on the cathode, and impurities will settle to the bottom of the electrolysis tank. In a similar way, electrolysis can be used to plate metal on any object that can be made to conduct electricity and hence can be used as the cathode in an electrolysis cell.