Content of sodium and lithium in aluminium during electrolysis of cryolite-based melts

The content of sodium and/or lithium in polarized and nonpolarized aluminium in contact with cryolite melts was determined in a laboratory cell. The cryolite-based melts contained 0 to 20 mass % excess AlF3 and 0 to 2.5 mass % LIF. The cathodic current density ranged from 0 to 0.5 A cm(-2). The lithium content in aluminium increases linearly with increasing concentration lithium fluoride in the melt. It also increases with increasing cathodic current density and decreasing cryolite ratio. On the other hand the sodium content decreases with increasing concentration of LIF in the melt. This effect is more notable at higher current densities.