GB760122A - Improvements in and relating to methods of and apparatus for the oxidation of coppersurfaces of objects of extended length - Google Patents

Abstract

760,122. Anodizing copper. GENERAL ELECTRIC CO. Sept. 21, 1953 [Sept. 20, 1952]. No. 26021/53. Class 41. To form an adherent film of black oxide on copper or copper-surfaced wire or strip suitable for the reception of a resinous insulating coating, the wire is passed through an electrolytic cell in which it forms the anode and which contains an electrolyte capable of producing anodic oxidation and the cell is subjected during the passage of any portion of the wire to at least one complete voltage pulse in which the voltage rises from below a value at which the anodeelectrolyte potential is 0.2 volt so that oxidation is initiated, to a higher value at which oxidation is augmented. Preferably the applied cell voltage in each pulse rises from 0.4 to 2.0, the last high voltage part of the pulse serving to improve the quality of the oxide formed while the anode and cathode are short-circuited between pulses. As shown, copper wire 7 is fed over rollers through an aqueous 13-40 per cent by weight solution of caustic soda or potash at 80-105‹ C. and is connected as the anode in a D.C. circuit including the electrolyte container 14 as cathode. The applied voltage is pulsed as shown in Fig. 1 by an interrupter 23 operated by a power-driven cam 24 which simultaneously closes switch 22 to short circuit anode and cathode, the resistor 18 being pre-set so as to result in the desired pulse shape. An automatic control responsive to changes in operating variables, such as the electrolyte temperature, may be employed to make small adjustments of resistor 18.