GB1413713A - Protecting iron surface from molten metal by adherent enamel layer - Google Patents

Abstract

1413713 Enamelling iron surfaces BAYER RICKMANN GmbH 13 April 1973 [15 April 1972] 17834/73 Heading C1M A process for the production of a protective enamel layer on a substrate comprising iron comprises applying to the substrate an enamel slip containing powdered aluminium and/or a powdered aluminium alloy in an amount 5- 75% by weight of the sum of the other solids of the slip, drying the slip, and storing the resultant composite substrate and slip at a temperature of 800-900‹ C. Part of the aluminium and/or aluminium alloy, e.g. 50% by weight, may be replaced by an equal weight of aluminium oxide. The particle size of the powdered aluminium or aluminium alloy may be 0À01- 0À10 mm. and this powder may be coated with a thin coating of oxide to retain even distribution in the slip. Uniform dispersion may also be retained by the addition of an oil or wetting agent. Further additives present in the slip, besides the frit, are clay, boric acid and sodium nitrate. Particularly suitable frits comprise in per cent by weight 33-50% SiO 2 , 0-25% B 2 O 3 , 15-35% Li 2 O+Na 2 O+K 2 O, 0-25% Al 2 O 3 +TiO 2 , 0-15% CaO+BaO, 0-10% ZnO + P 2 O 5 + ZrO 2 , 0-5% CoO + NiO + CuO, 0-7% F-, together with amounts of MgO, MnO, Sb 2 O 3 and Fe 2 O 3 . In the specific example the base enamel comprises in per cent by weight 44À4% SiO 2 , 3À4% Al 2 O 3 , 17À0% B 2 O 3 1À5% Li 2 O, 14À0% Na 2 O, 2À0% K 2 O, 5À8% CaO, 6À8% BaO, 0À2% CoO, 0À9% NiO, and 4À0% F-. The mixture of the slip and the aluminium and/or aluminium alloy may be applied to the substrate by immersion or spraying to the iron substrate which may be degreased and pickled prior to coating. In the specific example the composition is applied to pipe sections in a thickness of 0À15 Œ 0À03 mm.