Patent GB-770405-A (GB)
Title: Improvements in or relating to the electrodeposition of nickel
IPC: C25D3/12
Filed: 1954-10-22
Abstract: 770,405. Electrodeposition of nickel. UDYLITE RESEARCH CORPORATION. Oct. 22, 1954 [Aug. 6, 1954], No. 30547/54. Class 41. An acid nickel electroplating bath for producing a lustrous fine-grained deposit contains a small amount of chloral, bromal, or the corresponding mixed chlorobromo aldehyde, typically 0.2 to 0.4 g/l of the hydrate, and a small amount, typically 0.1 to 2.0 g/l, of a compound containing the group selected from methoxy-, ethoxy-, methoxyethoxy-, ethoxyethoxy-, and phenoxy-derivatives of ethyl acrylate; ethoxypropyl acrylates; phenyl acrylates; trimethyl aconitate; dimethyl fumarate or maleate; di-(methoxyethyl) fumarates, maleates or itaconates; coumarin; 3-chlorcoumarin. The alkoxy alkyl and alkoxyalkoxyalkyl radicals in the above compounds are preferably in straight chain form. Plating is effected with agitation at pH 3.5 to 5.2 and 50 to 60 C. Typically, to a sulphate-chloride bath containing per litre 150 to 300 grams of nickel sulphate, 20 to 60 grams of nickel chloride, 40-45 grams of boric acid is added either 0.2 to 0.4 gram of chloral hydrate and 0.6 to 1.0 gram of trimethyl aconitate; or 0.8 to 1.2 gram of di-(#-methoxyethyl) maleate, or 0.2 gram of coumarin or 3- chlorocoumarin; or 0.2 to 0.4 gram of one or both of chloral and bromal hydrates, and 0.3 to 0.5 of coumarin in sufficient concentrated sulphuric acid to dissolve it. Nickel sulphate, nickel chloride and nickel fluoborate baths may be used, preferably with boric acid as a buffer although formate, citrate, and fluoborate buffers may be used but desirably with boric acid as well. By increasing the temperature of the bath and the agitation, smaller quantities of the aldehydes are required. A metallic bright protective coating of nickel-cobalt alloy containing at least 10 per cent cobalt and preferably at least 50 per cent of nickel and having a thickness of 0.05 to 1 mil may be deposited prior to deposition of the usual chromium plate over a nickel plating of the above-mentioned kind and having a thickness of 0.5 to 2 mils, typically from a bath containing per litre 100 to 300 grams of nickel sulphate or chloride, 30 to 50 grams of cobalt sulphate or chloride, 40 to 45 grams of boric acid, and 0.1 to 3 grams of saccharin with or without a similar amount of benzene or toluene sulphonamide at a temperature of 40 to 70 C. and pH 2.5 to 4.8. Optionally this alloy bath may contain quinoline, iso-quinoline, their C-methyl or C- ethyl homologues, and/or the mono- or dihalogen derivatives as in Specification 698,998, or derivatives of these compounds or the analogous pyridine compounds in which an anion of a water-soluble acid and an aliphatic radical containing 1 to 4 carbon atoms are linked to the nitrogen atom as in Specification 743,726, when the pH may be as low as 1.5. Cobalt fluoborate may be used instead of the chloride or sulphate, and the cobalt salts may be replaced wholly or in part by ferrous or ferric salts in conjunction with fluoborate ions. Nickel-iron alloys may contain up to 40 per cent of iron while nickel-cobalt-iron alloys may contain up to 50 per cent of cobalt and iron together. For high resistance to atmospheric corrosion the iron content should not exceed 10 per cent, if the usual thin porous overplate of chromium is used. Specifications 525,847, 529,825, 622,761 and 704,185 also are referred to.