| 摘要 |
1299850 Electrolytic repair of chromium plated surfaces SIFCO INDUSTRIES INC 3 Dec 1970 [31 Dec 1969] 57475/70 Heading C7B A defective area in a chromium plated surface is repaired by a process comprising the sequential steps of mechanical cleaning, electrolytic cleaning, electrolytic activation, and electro-plating first with nickel and thereafter with chromium; in which a band of chromium is electrolytically removed from the chromium plated surface bordering the perimeter of the defective area, nickel is deposited over the defective area and an adjacent part of the band from which the chromium has been removed, and the chromium is deposited over the defective area, the band and an adjacent portion of the originally deposited chromium plate. The nickel may be a duplex coating comprising a layer of dull nickel followed by a layer of bright nickel. If necessary, copper may be deposited prior to the nickel. All electro-plating steps may be carried out using brush plating tools, that for the chromium deposition comprising a lead electrode and a ¢" thick polyester fabric or fibre pad covered with a polyester gauze; and that used for the other processes comprising a graphite electrode having a porous cotton tip covered by cotton gauze. In the example given the electrolytes used for cleaning the surface and for stripping the chromium band comprise sodium hydroxide and sodium metasilicate, and for activation comprises sulphuric acid. Copper is deposited from an aqueous solution of copper cyanide, potassium cyanide and potassium hydroxide; dull nickel is deposited from a bath including nickel sulphate and citric acid; bright nickel from a bath including saccharin; and chromium from a bath containing hexavalent chromium ions, e.g. prepared from chromic acid, sulphuric acid, trivalent chromium, trichloroacetic acid, and sodium hydroxide. |
