Patent GB-727748-A (GB)
Title: Improvements in electrodeposition of metals
Inventor: BLICKENSDERFER PHILIP STEMPEL
IPC: C25D5/00
Filed: 1952-06-23
Abstract: 727,748. Filling holes &c. in metal surfaces and uniting metal parts by electrodeposition CHAMPION PAPER & FIBRE CO. June 23, 1952, No. 15772/52. Class 41. In order to close an opening in a metal surface such as a pit 23, Fig. 3, in a chromium plating 22 on a metal base 21, a depression 30 whose depth is slight relative to its least width, is formed mechanically around the defect, the depression is provided with a continuous electrically conducting surface throughout its extent and metal is deposited electrolytically to fill the depression. The edges 31 of the depression may be rounded. Electrodeposition is confined to the depression by applying a resist elsewhere and/or by employing apparatus applied locally to form a cell. The anode 33 should be of smaller radius than the depression and is preferably nearer to the surface at the centre of the depression to avoid excessive buildup of the deposit at the edges. The deposit may be built-up beyond the original top surface and then mechanically cut down to the original level The bottom of the pit &c. 23 may be filled with lead or nickel or may be drilled to receive an iron plug; the cavity 30 may then be less deep For filling holes extending right through a metal sheet, a depression may be formed on one side as already described and the bottom of the original hole is filled with solder or other electrically conducting material. The depression is then filled by electrodeposition. If desired the sheet may then be turned over and a depression formed on the other side, the filling material being removed in the process, and this depression is filled by electrodeposition; excess metal on this side is then removed, together with excess metal on the other side if this had not been previously effected. A modified process comprises (i) filling a hole 214, Fig. 19, with conducting material flush with the surface of the sheet; (ii) blocking off a limited area 215 of the surface; (iii) electrodepositing metal on the exposed surface; (iv) turning over the sheet as shown at 216; (v) forming a depression 217 in which process the filling metal 214 is removed; (vi) filling the depression 217 by electrodeposition and removing excess metal on both sides down to the original surfaces of the sheet. For repairing a long slit in sheet metal or for uniting the discrete edges of abutting sheets, the two parts may be cemented to a rigid support and the intervening gap filled with conducting material, the subsequent procedure being as already described. Electrodeposition may be effected by application to the sheet &c. 21 of the apparatus shown in Fig. 7 comprising a cell body 40 provided with a washer 41, anode 33 and electrolyte supply and withdrawal means 55, 56, whereby turbulent flow is maintained through the cell. The cell body may be of glass or synthetic resin or of lead suitably insulated. The anode passes through a packing-ring 44 and washer 45 and may be adjusted by handle 46. The cell is held in place by a screw 57 mounted in a fixed member 52 and engaging a pressure block 50. Circulation of electrolyte is maintained by a suction pump whereby leakage of electrolyte is prevented. The surface being plated may be held in a vertical or inverted position. An arrangement for circulating electrolyte through a number of such apparatus in parallel between common reservoirs provided with temperature control means is described. A modified apparatus for filling elongated defects is also described. In treating defects in a nickel sheet, the depression formed as above described is polished and then treated anodically in a strong solution of sulphuric and phosphoric acids before electrodeposition of nickel. In filling cavities in chromium plating the chromium deposition bath may consist of (1) chromic acid 250 grams, boric acid 30 grams per litre with sulphate ions 1/100 of hexavalent chromium ions; (ii) chromic acid 250 grams per litre, sulphate ions 1/85 of hexavalent chromium ions. The article under treatment may be connected first as anode for a short time, then as cathode with current density slightly less than the minimum required for plating, and finally as cathode at a higher current density. Specification 727,789 is referred to.