Abstract
	To design a Hall-Héroult cell with a prolonged lifetime, it is necessary to understand the properties of the cathode carbon material as well as the behavior of its sodium content and the contacting electrolyte under the prevailing electrolysis conditions. Penetration of the carbon cathode material by both sodium and the electrolyte results in various adverse effects, including cathode swelling and crack propagation, cathode heaving, carbon conversion and cathode disruption. These effects all have decisive negative influences on the cell lifetime and in many cases could, in the worst cases, lead to cell destruction and serious process economic losses.
	A lot of research to minimize the sodium penetration into the carbon cathode block, thereby minimizing the effect of cathode swelling has been carried out. Among others the most known technique – and one which much effort has gone into – is the utilization of titanium diboride as coating on carbon cathode materials and carbon – titanium diboride composites.
	A concise overview of the cathode failure phenomena, caused by sodium penetration into the cathode carbon block material, is provided, along with some suggested methods for carbon cathode block improvements, so that the life time of an aluminum electrolysis cell is prolonged, and the expense of aluminum production reduced, in addition to lessened impact of the “spent” potlining on the environment.