The trend in the aluminium smelting industry today is to operate cells with graphitized carbon cathode linings, increased current density and acidic bath chemistry. The resulting problem is an accelerated wear of graphitized cathode blocks, thought to be caused by formation and subsequent dissolution of Al4C3 at the cathode lining surface. The cycle of formation and subsequent dissolution Al4C3 is recognized as one of the most important mechanism causing pothole and surface wear, which results in limiting of the cell lifetime and loss efficiency. A special laboratory test method was developed to elucidate the mechanism of Al4C3 formation in electrolytic cell. The Al4C3 formation in the region between the carbon surface and aluminium as well as between the carbon surface and electrolytic bath has also been studied using X-ray diffraction, as well as optical and scanning electron microscopy. Solid Al4C3 layer was observed at the carbon surface. A possible mechanism which explains the presence of Al4C3 at the metal-bath interface is the transfer of dissolved carbide in the bath from metal-carbon interface.