GB1459995A - Vitreous enamel coatings - Google Patents

Abstract

1459995 Treating enamel coatings BRITISH GAS CORP 15 Feb 1974 [20 Nov 1972] 53567/72 Heading C1M A method of treating vitreous enamel, in the form of a coating on a substrate, comprises decomposing a compound comprising at least one metal ion, the metal ion being such that when incorporated into the enamel surface it improves the microhardness of the surface (measured by the Vickers method) by at least 10%, the compound being decomposed to the corresponding metal oxide in or on the enamel surface to increase the surface strength and hardness. The metal ion may be Sn, Cu, Ni, Al, Co, Ce, V, Mn, Zr, Ti or Zn, and the compound preferably decomposes at 200-800‹ C. In one embodiment metal halide vapour (e.g. a halide or Cu, Al or Sn) is introduced into a furnace in which it decomposes to the oxide, which is deposited on the enamel. Alternatively, the enamelled article may be immersed in a solution or dispersion of an organo-metallic compound, removed and drained, and heated to decompose the organometallic. Also, a pre-heated enamelled article (e.g. at 400-800‹ C.) may be sprayed with a solution or dispersion of the organo-metallic, the compound pyrolysing to form the oxide on contacting the surface. Also, an enamelled article may be sprayed with organo-metallic and the surface then subjected to oxidation. The organometallic compound may be diisopropyl triethanolamine titanate, or an alkyl titanate, vanadate, zirconate, stanate, zincate or aluminate. The vitreous enamel preferably is one which has been fired at 700-850‹ C., or a titania-opacified white enamel. The invention may be used in providing an improved enamel coating on gas ovens or cookers. A wax coating (e.g. polyethylene wax, silicone wax or carnuba wax) may be provided over the enamel.