GB712314A - Method of and apparatus for a uniform electrolytic internal chromium plating of tubes - Google Patents

Abstract

712,314. Electro-plating. ELECTRO METAL HARDENING CO. SOC. ANON. Feb. 7, 1952, [Feb. 8, 1951.] No. 3114/51. Class 41. In the internal chromium-plating of a rifled tube an anode is employed, the cross-sectional cenfiguration of which is the inverse counterpart of the rifling of the tube, and the tube is rotated relatively to the anode. Both the tube and the anode may be rotated, the rotations being at different speeds or in opposite directions. The velocity of rotation may be non- uniform, e.g. the rotation may be interrupted and resumed one or more times during each complete revolution. Interruption or retardation of the rotation may be effected at times when portions of the inner tube surface which would otherwise be less intensely plated are positioned closest to the anode; the interruptions or retardations may also be timed to produce a reinforced coating at desired portions. As shown the rifled gun barrel 4 is mounted between, and the anode 6 is mounted in, fitting elements 8, 10; the rifled formation of barrel and anode is not shown. Electrolyte is supplied to the barrel by conduit 12 and leaves by conduit 14. The upper element 10 is rotatably mounted in a container 2 and is driven by means of a cog-wheel 26. The lower member 8 is fixedly mounted in the container and is provided with a rotatable bushing 24 in which the lower end of the barrel 4 is supported. Ball bearings 20, 22 are provided in the container 2. The outer surface of the bushing is provided with a helical thread of considerable pitch, this tending to press down electrolyte which would otherwise leak upwardly. Electrolyte from the barrel discharges at the top into an annular groove in the fitting 10 and thence to the outlet 14. The outer surface of the element 10 is provided with helical grooves on either side of the annular groove to prevent leakage. Any electrolyte which may leak into the container 2 is discharged by conduit 16. The upper anode terminal 7 may be swung away to permit the anode to be inserted in or removed from the container.