Corrosion resistant refractory mix

A corrosion resistant refractory mortar or castable mix is provided comprising a particulate mixture capable of mixture with water to form a castable refractory or mortar having enhanced corrosion resistance to molten aluminum which is particularly useful in the production of ultra high purity aluminum. The mixture consists essentially of 10 to 34 parts by weight calcium aluminate, 1.5 to 10 parts by weight of a zinc borosilicate frit and 60 to 88 parts by weight alumina. The zinc borosilicate frit consists essentially of 50 to 60% by weight zinc oxide, 20 to 40% by weight boron oxide, 8 to 12% by weight silicon oxide and 0 to 10% by weight aluminum oxide with less than 0.5% by weight of other impurities. The refractory mix contains not greater than 1% by weight impurities.