The invention is directed to a method of providing a protective coating composition that protects a refractory wall or lining from chemical attack by molten aluminum and molten alkali metals. The method includes the steps of coating a refractory wall or liner with an aqueous protective composition that includes, by weight of the solids, about 20-90% Al2O3 (excluding calcined alumina), about 15-55% SiO2 and about 1-15% of a metallic non-wetting agent; and evaporating the water before contacting the protective coating with the reactive molten metal.