Andalusite: An amazing refractory raw material with excellent corrosion resistance to sodium vapours

The chemical attack of alumina refractories by sodium vapours is far from been completely understood. In order to contribute to a better knowledge of this attack, a laboratory test was developed to simulate the sodium gaseous corrosion of different raw materials and refractories. Corrosion of alumina raw materials by sodium vapours is due to a dissolution–precipitation process by a Na2O rich liquid phase. The gaseous corrosion strongly depends on the microstructures and the assemblage of phases in alumina raw materials. Fire clay and andalusite raw materials exhibit very high corrosion by Na vapours. In spite of an initial high silica glass content, and as a result of trapping of the main part of the glass in the capillary network of the mullite composite crystal, mullitised andalusite leads to excellent corrosion resistance which is close to monocrystalline fused mullite. Consequently, The use of mullitised andalusite particles in the matrix of alumina refractories limits the liquid phase formation during corrosion by sodium gas. These experimental results are in agreement with thermodynamic calculations.