GB761372A - Improvements in and relating to methods of electrolytic oxidation of copper - Google Patents

Abstract

761,372. Anodizing copper wire. GENERAL ELECTRIC CO. Sept. 18, 1953 [Sept. 20, 1952], No. 25857/53. Class 41. To form a black oxide coating on a copper or copper plated wire or strip, the wire as anode is passed through a series of copper anodizing cells, in the first group of which the potential applied to the cell is not greater than the upper critical value of the anode-electrolyte potential of 0.2 volt for starting oxidation, while in the second and third groups the applied potential is successively greater and increase the thickness of the coating and improve its quality respectively, the coated wire then being washed and dried; and if desired polished. Preferably the voltages applied to individual cells in the second group are equal or are successively only slightly greater while the increased voltage applied in the third group acts on the oxide-coated wire for a shorter period than is occupied by passage of the wire through the first two groups. As shown, a copper wire 5 is fed through a series of cells 6 ... 10 separated by insulating spacers apertured to receive the wire freely and to permit ready flow of an aqueous 15-45 per cent by weight solution of caustic soda or potash, the wire being connected as the anode while the cathode connections are made to the cell containers. For this last purpose stand pipes 16 on each cell for the escape of gases evolved in electrolysis serve as cathode connections and are held at potentials appropriate to the group to which the cells belong so that the wire is subjected over its whole travel to an electrolysing voltage as shown in Fig. 1. The electrolyte is held at a temperature of 80-105‹ C. by circulating it by means of a pump 18 over an external heater 22, a now meter 23 being also provided. Instead of a single wire, two or more parallel wires or an interwoven multistrand wire may be similarly anodized. The oxide-coated wires are suitable for coating with resinous compositions as in Specification 761,373. Specification 760,122 also is referred to.