GB504026A - Improvements in or relating to the polishing of nickel applicable also to the production of decorative or other designs upon the surface - Google Patents

Abstract

504,026. Brightening nickel by electrolytic treatment. PRISTON, H. R., HOTHERSALL, A. W., and HAMMOND, R. A. F. Sept. 17, 1937, No. 25313. [Class 41] A bright surface is produced on a nickel or nickel-plated article by anodic treatment in sulphuric acid of more than 60 per cent concentration, smoothing being effected by selective attack on raised points. Formation of streaks is prevented by agitation of the electrolyte or of the work. It may also be prevented by addition to the electrolyte of one of the following substances which serve to reduce the surface tension or viscosity of the anode film or to reduce the size of the gas bubbles : (i) a sulphonate of the aromatic hydrocarbons such as sodium toluene or sodium benzene monosulphate (e.g. 2-4 gms per litre); (ii) glycerine (e.g. 200 ml per litre) ; (iii) nitric acid (e.g. 40 ml per litre); (iv) chromic acid (sufficient to saturate the solution). The treatment is preferably applied to nickel platings of small grain size deposited from the following baths : (i) nickel sulphate NiSO 4 .7H 2 O 120 gms., ammonium sulphate 21 gms., potassium chloride 8 gms., water to 1 litre ; (ii) nickel sulphate NiSO 4 .7H 2 O 240 gms., nickel chloride NiCl 2 .6H 2 O 4.5 gms., sodium formate 35 gms., water to 1 litre. The surface may be treated locally to produce a design by application of a resist.