Corrosion mechanism of MgAl2O4-CaAl4O7-CaAl12O19 composite by steel ladle slag: Effect of additives

Corrosion behaviors and corroded microstructures of MgAl2O4-CaAl4O7-CaAl12O19 composites containing various additives (ZrO2 and TiO2) against steel ladle slag (containing CaF2) were investigated using a reaction test method at 1600 °C. Thermodynamic calculation, based on the Al2O3-CaO-MgO phase equilibrium diagram was used to further reveal the corrosion mechanism. The attack of the liquid slag on the composite substrate was found to take place through an interdiffusion mechanism, producing the precipitation of spinel in the slag and a continuous layer of calcium dialuminate at the interface. This composite showed a high total corrosion depth due to the high porosity of the substrate and the high fluidity of the slag. Fortunately, the addition of ZrO2 and TiO2 can greatly improve the slag corrosion resistance by increasing the viscosity of the slag at an earlier stage. Besides, the highly dense microstructures also improved the corrosion resistance against the liquid slag, and thus suppressed the slag penetration. It was also found that the CA6 grains with low aspect ratios are more difficult to be wetted and dissolved by the slag.