GB398825A - Improvements in the electrolytic production of insulating layers on metals - Google Patents

Abstract

398,825. Electrolytic treatment of metallic surfaces. COURSEY, P. R., 67, Queen's Road, Richmond, Surrey, MARCUS, C. H., 15, Stanley Street, Wilkes-BarrÚ, Pennsylvania, U.S.A., and DUBILIER CONDENSER CO. (1925), Ltd., Victoria Road, North Acton, London. Jan. 16, 1932, No. 1311. [Class 41.] Insulating-coatings are produced on aluminium and other metals by electrolytic treatment 'in two stages, the first being conducted at low voltage, for example 20-30 volts, and the second in a different electrolyte at a relatively high voltage, for example, 750-1000 volts. Dilute sulphuric acid may be employed as electrolyte in the first stage and a solution of ammonium borate in the second. In the apparatus shown strips A, B are guided by rollers through a vessel 11 in which they are subjected to alternating current drawn from one secondary winding of a transformer. Strips C, D are passed through a vessel 12 and connected to a similar winding. The midpoints 3, 6 of the two windings are connected through a high-voltage winding 7. By passage of the strips A, C through vessel 13, and of the strips B, D through a vessel 14 all of the strips are subjected to high-voltage treatment. The low-voltage and high-voltage treatments may each be performed in two or more stages employing different voltages and electrolytes by suitably increasing the number of strips treated. In one or other of the stages direct current, may be employed, chokes and condensers being connected to separate the two circuits. Washing or other treating baths may be provided before, between and after the electrolytic baths. The coated articles may be used in the production of electrolytic or other electric condensers and insulated coils.