The corrosion resistance of alumina-mullite-zircon refractories in molten glass

Abstract

Corrosion measurements on a set of alumina-mullite-zircon refractories have been carried out using a static crucible test consisting of a "hole in a block". Rates of corrosion of the refractory at 1370 degreesC for 72 h by a standard soda-lime glass were evaluated by measuring selected dimensions within the hole, flux line loss, and the thickness of refractory penetrated by the molten glass. The extent of corrosion decreased with increasing refractory zircon content, and increased with increasing porosity. Wetting of the refractory by the glass decreased with increasing zircon content. Porosity and wettability are therefore believed to be major factors determining the susceptibility to penetration of the refractory by the glass, and thereby controlling the rate of corrosion. Microstructural features of the interfacial zone were examined by SEM: zirconia derived from the zircon appears to be much less reactive towards the molten glass than alumina. Undissolved zirconia particles may therefore be particularly effective in providing physical and energy barriers to penetration of the refractory pores by molten glass.