A structure protected by a ceramic coating is prepared by providing a substrate having a surface, and depositing a layer of a sacrificial ceramic precursor material, preferably silica, onto the surface of the substrate. The method further includes furnishing a reactive gas, preferably an aluminum-containing gas, that is reactive with the sacrificial ceramic to produce a protective ceramic different from the sacrificial ceramic, and contacting the reactive gas to the layer of the precursor material to produce a protective ceramic layer.