Analysis and interpretation of refractory microstructures in studies of corrosion mechanisms by liquid oxides

The refractories must not only resist high temperatures but also corrosion by liquid oxides. This corrosion involves phenomena of dissolution and precipitation of new crystalline phases. The study of the microstructures of corroded refractories provides essential information. However, the interpretation of the microscopic observations is difficult. Indeed, because of the crystallization of liquid glasses during cooling, the mineral phases observed at room temperature are not representative of those observed at high temperature. The concept of local thermodynamic equilibrium and the use of the phase rule makes it possible to interpret the microstructures of corroded refractories, to explain the observed mineral zonation and to quantify the composition of the liquid phase at high temperature from chemical profiles established by SEM. Experimental data from corrosion of high alumina refractories will illustrate and validate this theoretical approach.