GB580688A - Improvements in or relating to enamel compositions suitable for application to aluminium and aluminium alloys - Google Patents

Abstract

580,688. Vitreous enamels. DU PONT DE NEMOURS & CO., E. I., and DEYRUP, A. J. Aug. 13, 1943, Nos. 13147/43 and 5980/44. [Class 56] A vitreous enamel particularly for the surface of aluminium or aluminium base alloys comprises essentially 25-65 per cent PbO, 20-35 per cent silica, 1-15 per cent TiO2 and a total of 10-30 per cent of one or more of the oxides of sodium, potassium and lithium. Not more than 9 per cent of LiO2 should be present. In addition.one or more of the following may be present :-up to 10 per cent of B2O3, up to 7 per cent of ZrO2, from 0.5-5 per cent of antimony oxide expressed as Sb2O3, and from 1-15 per cent of a ceramic pigment, e.g. opacifying agents such as sodium zirconium silicate or coloured pigments. Other oxides, e.g. up to 5 per cent of cobalt oxide to give a blue colouration or copper oxide to give a green colouration, may be present, but fluorides should not be present. The batch is mixed and melted and run into water to make a frit which is subsequently pulverized dry or with a non-aqueous liquid such as methanol, the pigments being added during grinding. The enamel may be mixed with methyl cellulose 0.75 per cent, sodium chloride 1 per cent, octyl alcohol 0.05 per cent and water 90.2 per cent and sprayed on the metal or with ethyl alcohol 4 per cent soya lecithin 0.25 per cent and terpineol 95.75 per cent and stencilled on. Alternative vehicles are methanol or turpentine 95 per cent and dammar varnish 5 per cent. After application and drying the enamel is fired at 400-550‹ C. Heat treatment of the alloy may be carried out after the enamel has been fired. Specification 580,689 is referred to.