GB1179623A - Electrolytic Metal Finishing - Google Patents

Abstract

1,179,623. Method of electro-plating or electro-polishing. ALBRIGHT & WILSON (MFG.) Ltd. March 8, 1968 [March 10, 1967],No.11331/67. Heading C 7B. A composition for use in electro-plating or electro-polishing comprises an aqueous solution of a salt or acid or alkali as an electrolyte and inert non-metallic beads having a minimum diameter between 0À5 and 10 mm in an amount such that the ratio between the true volume of the beads and the volume of liquid within which the beads are contained (i.e. the total volume of liquid and beads minus the volume of the beads, is at least 0À5:1). The beads may be of glass; mica; thermo-plastic material, e.g. polyethylene, polypropylene, polystyrene or polyvinyl chloride; graphite; rubber; polyester or polyamide. In shape the beads may be spherical, hemi-spherical, cubic, ovoid or polyhedral, and may have a specific gravity greater, equal or less than that of the electrolyte. Articles which may be treated include iron, steel, zinc, nickel, brass, alloys thereof and plastics coated with a metallic layer. The present method may be used for depositing metal from baths containing silver cyanide, chromic acid, cadmium sulphate or cyanide, copper or zinc sulphate, cyanide or pyrophosphate, or nickel sulphate, chloride (e.g. Watt's bath) or sulphamate. The latter bath may also contain nickel chloride and naphthalene trisulphonic acid. The method may also be used in the electrodeposition of brass or bronze; in the electropolishing of copper, brass and stainless steels using a phosphoric acid electrolyte which may also contain sulphuric acid, chromic acid or alcohol, e.g. a phosphoric acid/sulphuric acid bath containing diethyl phthalate as a brightener, or in the electro-polishing of aluminium using an alkaline bath, e.g. caustic soda. The baths may contain brightner additives and/or levelling agents. The article may be inserted into the electrolyte, or may be rested upon the surface of the electrolyte on top of which the beads are floating. The resultant surface may receive subsequent treatment, e.g. anodizing or coating with a varnish or laquer, or a conventional electro-polish.