The Mechanism of Corrosion of Refractory Materials by Molten Glass

JSGT 1948 V32 T046-T061

Fom the evidence afforded by the petrological examination of specimens, taken from various positions in glass tanks and pot furnaces, the mechanism of refractory corrosion is discussed. It is postulated that the initial attack of refractory materials is brought about by the vapour of volatile oxides. These oxides tend to reduce the temperature at which the peritectic reaction: mullite –> corundum + siliceous glass, occurs, in silica–alumina refractories. The size of mullite crystals is also considerably increased by reactions with these vapour phases, giving rise to substantial reductions in the mechanical strength of the crystalline network. Similar results occur where local impurities are present in the original material. The addition of fluxes to reduce the porosity and permeability of refractories is therefore deprecated. The reduction in strength of the crystalline network, together with the increased mobility of the glassy matrix, greatly facilitate the removal of material by glass erosion. Finally it is stressed that refractories of low permeability are likely to be resistant to attack by molten glass, by virtue of their smaller penetration by vapour phases. This adds a further property to be considered together with the other well-known requirements for refractory materials possessing high resistance to corrosion by glass.

K. E. Seal