The effect of SrSO4 and BaSO4 on the corrosion and wetting by molten aluminum alloys of mullite ceramics

In order to improve the corrosion resistance of aluminosilicate refractories by molten aluminum, SrSO4 and BaSO4 powders were used. Mullite substrates with and without addition of 20 wt.% SrSO4 or BaSO4 were sintered at 1400 °C for 6 h. Corrosion and wetting experiments with molten pure Al and Al–7.5Si were carried out at 900 °C for 24 h and 900 °C for 2 h, respectively. The corrosion layer was thicker in the mullite sample (≥2 mm) than that of the SrSO4- or BaSO4-containing mullite samples (<50 μm). The contact angles for mullite samples containing SrSO4 or BaSO4 were higher (≈118° and 149°) than those of the mullite sample (≈109° and 127°), with both pure aluminum and Al–7Si alloy. This increase in the contact angle improves the corrosion resistance in mullite samples by means of non-wetting effect.