GB637755A - Improvement in processes for coating metal surfaces - Google Patents

Abstract

637,755. Enamelling ferrous metals. POOR & CO. Nov. 24, 1947, No. 31107. Convention date, June 18, 1940. [Class 56] In the process of enamelling ferrous metals a bond coat containing an acid solution of SbCl 3 , AsCl 3 , and SnCl 2 is applied to the metal. The bond dip solution is made by dissolving commercial Sb 2 O 4 in cold 18‹ Baume HCl in the proportion of 0.6 pound for each gallon, then adding one part As 2 O 3 for every thousand parts of Sb 2 O 4 and finally adding a solution of SnCl 2 in strong HCl until the solution changes colour from yellow or amber to colourless or pale green. The ferrous sheet is then cleaned in a boiling alkali cleaner for 15-30 minutes, rinsed in water, pickled in 6-10 per cent by weight H 2 SO 4 for 15 to 45 minutes at 140-160‹ F., placed in the bond dip solution, rinsed, and neutralized in a bath containing borax and soda ash at 140‹ to 180‹ F. for 2 to 8 minutes. The As 2 O 3 acts as a dipolarizing agent, and the SnCl 2 reduces any ferric iron to the ferrous state. The glass may contain the following parts by weight: feldspar 20.9, borax 40.2, Silicon 22.9, soda ash 5.1, sodium nitrate 4.8, fluorspar 6.1, and after fritting is dried and milled, and to give a light grey coating the following parts by weight are added: 100 parts of frit, clay 7, opacifier 3, illmenite #, black iron oxide 5/16, borax ¥, water 40. The metal is coated by spraying or dipping &c., dried, and fired at from 1260‹ to 1460‹ F.