Reduction in Aluminum Alloy Attack on Aluminosilicate Refractories by Addition of Rare-Earth Oxides

Several aluminosilicate compositions were tested for molten 7075 aluminum alloy attack with and without the addition of 10% Na₂CO₃. The extent of corrosion was proportional to the silica content of the refractory and especially of the matrix phase. The addition of rare earths up to 15% by weight to the aluminosilicates virtually eiiminated corrosion. Bastnasite, a rare-earth concentrate, was found to be a more effective additive at low concentrations than either CeO₂ or La₂O₃ alone in rendering the aluminosilicates corrosion resistant.