A novel method to improve the slag corrosion resistance of the MgO-C refractories was developed by the application of voltage between MgO-C refractories and molten slag. With applied voltage, the corrosion rate of the anode and cathode decreased from about 15.0 to 8.9% and 1.1%, respectively. The electrochemical reactions that occurred between the MgO-C electrodes and the molten slag promoted the adherence of the reduced metals at this interface. The reduced metals created a barrier that protected the MgO-C cathode from further attack of the molten slag. The results suggest that the applied voltage induced the migration of oxygen ions to the anode and that this reduced the dissolution of the anode.