Our group proposes a new titanium smelting process via Bi-Ti alloy. This process is comprised of reduction of TiCl4 by Bi-Mg liquid alloy, separation of Ti from Bi by distillation, and Mg electrolysis. In this study, the Mg electrolysis with Bi-Mg liquid alloy cathode was investigated. We firstly measured the IR-corrected polarization curves on graphite and Bi-Mg liquid alloys by the current interruption method. The results indicated that the Bi-Mg alloy cathode can reduce the electricity consumption of the Mg electrolysis. In addition, from the relaxation curves on graphite and Bi-Mg alloys, the concentration overpotential on the Bi-Mg alloy is mainly due to mass transfer of Mg from the electrode/molten salt interface to the liquid alloy bulk. At current densities higher than 300mAcm(-2), Mg-rich solid phases such as Bi2Mg3 and/or pure solid Mg are assumed to be deposited on the Bi-Mg liquid alloy cathode. Finally, we estimated the electricity consumption of the Mg electrolysis in the new smelting process based on the measured overpotentials, assuming that Bi-Mg liquid alloy cathode is stirred sufficiently and a low current density, 275mAcm(-2), is applied. Under these conditions, the total electricity consumption of the Mg electrolysis in the new process will be lower than that in the Kroll process when the anode-cathode distance is smaller than 8cm.Graphic abstractIR-corrected polarization curves of (a) Mg2+ reduction on graphite and Bi-Mg liquid alloys and (b) Cl-2 evolution on graphite in MgCl2-NaCl-KCl at 550 degrees C were measured by the current interruption method, and electricity consumption of Mg electrolysis in the new Ti smelting process was estimated from these results. [GRAPHICS] .