Water vapor corrosion of mullite containing small amount of sodium

The corrosion test for hot-pressed mullite bulk was performed in static state water vapor environment at higher temperatures such as 1300 and 1500 °C. After corrosion test, the samples exhibited weight gains with a rate of 6.60 × 10−6 and 8.42 × 10−5 g/cm2 h at 1300 and 1500 °C, respectively. Microstructural and phase analyses revealed, corundum phase formed on mullite bulk surface and a large amount of pores were formed near the bulk surface. Crystalline corundum was directly grown from silica rich sodium containing aluminosilicate phase.