The present invention provides a process for providing on the surface of a substrate an adherent phorphorous acid-based coating layer, the method comprising contacting said surface with a carrier conveying a coating composition comprising an acid selected from the group consisting of phosphoroic acids, organo-phosphoric acids, phosphonic acids, and mixtures thereof, at a sufficient temperature and for a sufficient time to bond at least a portion of the acid in the compositon to the oxide surface.