GB610529A - Improvements in or relating to the coating of objects by cathodic disintegration - Google Patents

Abstract

610,529. Depositing substances by discharges. EDWARDS & CO. (LONDON), Ltd., W., and HOLLAND, L. A. Sept. 7, 1945, No. 23128. [Class 39 (i)] Apparatus for coating objects by cathode disintegration comprises a cathode 8, Fig. 1, one side of which faces the object supporting means 10 and the other side of which faces an anode surface 6, and the distance between the cathode 8 and anode 6 is such that the latter lies in the cathode dark space so as to suppress cathode disintegration in this direction. The members 2, 3, 6 are all maintained at anode, i.e. earth, potential; the envelope is sealed by a rubber gasket 5. The table 10 may or may not be at anode potential. When the top of the envelope 3 is flat the screen 6 can be dispensed with. In another embodiment, Fig. 2, the electrodes 8a, 8a are connected across an alternating current supply; 10a, 10a are the object supports. In further arrangements, Figs. 3, 4 (not shown), the electrodes and object may be concentric cylinders. In a further arrangement, Fig. 5, the cathode supporting members 20, 21, 22, 23 are surrounded by tubular anode supporting members 25, 26, 27 within the " dark space " distance. An annular anode plate 6f lies in the cathode dark space proper. In all forms the electrodes may be foraminous, and the anode member within the cathode dark space may have a different potential from that of another anode present. The cathode is preferably of brass and is coated with the material to be deposited only on the side thereof facing the object. The electrode spacing is <1>/16 to <5>/16 inches at voltages between 500-10,000, the gas pressure being 0.01-2 mms. Hg. The Provisional Specification states in addition that when the envelope wall is of metal its inner walls except those within the cathode dark space are covered with insulating material. The object may be coated with a noble metal.