GB665880A - Improvements relating to vitreous glazing or enamelling compositions and their application to metal surfaces - Google Patents

Abstract

665,880. Enamels. FRASER, R. P., and CIANCHI, A. L. June 1, 1949 [June 1, 1948], No. 14742/48. Class 56. Vitreous enamels for bonding to magnesium and magnesium base alloys have a fusion or maturing temperature below 550‹ C. and a coefficient of expansion greater than 20.0x10<SP>-6</SP> in the temperature range 10‹-100‹ C:, the main constituents calculated as whole percentages being, R 2 O 18-30, RO 35-50 of which 20-40 is PbO, R 2 O 3 5-17, RO 2 17-40 of which 17-30 is SiO 2 , where RO 2 stands for SiO 2 with or without other Group IV oxides, R 2 O 3 stands for the oxides of B, and Al, R 2 O stands for the oxides of Na, K, and Li, and RO stands for the oxides of Pb, Mg, Ca, ZN, Sd, Ba. The ratio RO 2 +R 2 O 3 /R 2 O+RO-including PbO) is less than 1. TiO 2 and/or ZrO 2 may be added before firing, or as a mill addition during grinding after firing or at both stages. To obtain a suitable white base enamel Mo 3 O 4 or soluble Mo salts such as the molybdate of NH 4 , Na, or K may be added (approximately 2-5 per cent) and to obtain best results a further 1-5 per cent is added to this batch in the mill after firing. The dry batch compositions and the first compositions in weight and mols per cent of five examples are given. The ingredients may be added as oxides, carbonates, nitrates, or silicates, and at least some of the Al 2 O 3 is added as potash felspar. The batch is mixed, melted, fritted in water, and ground with the addition of colouring oxides or opacifiers. The first is formed into a slip with water, applied, and stored below 600‹ C., or may be applied by the method and apparatus according to Specification 648,279. The slip may include two frits of different softening temperature or colour, or a ground frit may be mixed with powdered silica or the like to produce a matt finish. Specifications 642,104, 648,279 and 665,903 also are referred to.