C23C 28/042

Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups [CPC: C23C2/00] - [CPC: C23C26/00] or by combinations of methods provided for in subclasses [CPC: C23C] and [CPC: C25C] or [CPC: C25D] only coatings of inorganic non-metallic material {including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides}