Corrosion protection of MgO electrodes at 1400 °C

MgO-electrodes were polarised at voltages of up to 10 V in a synthetic lime–alumina–silicate slag at 1400 °C. Cathodic corrosion protection was obtained at voltages ⩾8 V, whereas anodic decay was accelerated manifold. The protective effect was mainly achieved by electrostatic alteration of the slag composition at the electrode boundary. This was primarily caused by the rapid migration of mobile Ca2+-ions and their accumulation at the slag/electrode interface. Consequently, the saturation concentration of CaO in the melt was reached and the precipitation of the CaO-containing phases merwinite, melilite and dicalciumsilicate occurred.