Inert, wettable cathodes have a significant potential for improving the Hall-Héroult electrolysis cell. TiB2 is considered the most promising inert cathode material, having good wetting properties towards aluminium. Allowing reduced ACD will result in lower energy consumption and, at the same time, potentially extend the cathode lifetime. However, the implementation of TiB2 is not straight forward, mostly due to the challenges of understanding the degradation mechanisms. Sodium vapour, which has proved to have great impact on traditional carbon cathodes, has drawn less attention for TiB2 materials. Thermogravimetric tests with various sodium vapour activities has been used to study the effect of sodium vapour on commercial TiB2 materials. Further, the chemical stability of TiB2 towards sodium and transport property of sodium in TiB2 materials have been investigated by atomistic calculations based on density state theory. Finally, a possible degradation scheme of TiB2 materials in environments subject to sodium exposure is proposed.