Use of phase diagrams in studies of refractories corrosion

Abstract

Typical applications of phase diagrams to specific problems of refractories corrosion are highlighted. Saturation solubilities of refractories components in molten slags can be estimated using existing phase diagrams. These can then be used to predict the corrosion behaviour, and qualitatively compare the corrosion resistance, of a refractory in different slags or different refractories in the same slag. If the slag is not saturated with refractories components, using relevant phase diagrams, the conditions under which solid reaction product phases form at refractories/slag interfaces can be predicted, which assists understanding of direct and indirect dissolution. By checking the compatibility between impurities or additives and refractories components at high temperatures, their influence on corrosion resistance can be predicted, aiding their selection. Phase diagrams also reveal that atmosphere affects refractories corrosion resistance by altering the valence of some components (in particular, iron oxide) in the refractories and/or slags. The compatibility between refractories and slags indicates the corrosion resistance of different refractories, assisting refractories selection for specific applications. Finally, phase diagrams can be used to assist design of refractories composition. Repeated experimental corrosion test results show good agreement with phase diagram predictions. Therefore, use of the information which is available in existing phase diagrams can reduce the need for expensive and time consuming experiments to evaluate high temperature corrosion of refractories (and other ceramics).