GB634262A - Improvement in coating of metal surfaces - Google Patents

Abstract

634,262. Enamelling. POOR & CO. Nov. 24, 1947, No. 31108. Convention date, May 9, 1940. [Class 56] In the process of enamelling ferrous metals the sheets are first treated with a self-bonding milled slip containing a metallic borosilicate having a fusing point between 1000‹ F. and 1260‹ F. and a solution of ferric sulphate decomposable below the fusion temperature of the glass. In examples, glass frits are formed from the following parts by weight: (1) litharge 73.6, boric acid 11.1, silica 15.3, or (2) litharge 46.8, boric acid 9.45, silica 13.10, calcium carbonate 15.7, fluorspar 10.20, zinc oxide 4.75, and when the frit is milled 4 ozs. bentonite, 6 ozs. illmenite, 4 ozs. black iron oxide and 40 pounds water are added to every 100 pounds of frit. ¢ to ¢ vols. of 20 per cent aqueous solution of ferric sulphate is then added to every 100 vols. of frit, and sodium nitrate solution may also be added in the proportion 1 c.c. of 20 per cent aqueous solution of nitrate to 100 c.cs. of milled slip. The metal articles are first cleaned in an alkaline bath, rinsed, pickled in acid, rinsed, neutralized and dried, or sand blasting may replace the cleaning and pickling. The article is then coated with the enamel slip by spraying or dipping &c., dried and fired. The firing temperature, for example (1) is 1070‹ F., for example (2) 1120‹ F., and in any case does not exceed 1260‹ F., and therefore the base metal does not warp &c. The Specification as open to inspection under Sect. 91 comprises also the use of other oxidizing agents, such as ferric chloride, potassium dichromate, sodium dichromate, and sodium sulphate. This subject-matter does not appear in the Specification as accepted.