ELECTROPLATING OF SMOOTH, SEMI-BRIGHT GOLD DEPOSITS

摘要

1,200,110. Electro-deposition of gold and gold alloys. SEL - REX CORP. Aug.1, 1967, [Sept.7, 1966], No. 35230/67. Heading C7B. Small parts of irregular shape are uniformly plated with gold, e.g. by barrel plating, by electro-deposition at a current density of 0À1 to 10 amp/sq.dm. at 20‹ to 90‹ C from an aqueous bath consisting of Gold (added as alkali metal gold cyanide) 1 to 75 g/l Conducting and buffering compounds 5 to 400 g/l Thallium (added as a watersoluble compound) 0À001 to 25 g/l Alum 0À100 g/l the pH being adjusted to lie within the range of 3 to 6 e. g. with phosphoric acid. By "alum" is meant the hydrated double sulphates of ammonium the alkali metals or thallium with those of aluminium, chromium or gallium. The thallium compound used may thallous or thallic sulphate, thallium chloride nitrate or fluosilicate or thallium (I) alum. The buffering compounds may be partially neutralized weak stable organic acids or alkali metal phosphate. In examples the gold is supplied as the potassium double cyanide, thallium as the sulphate and the bath is buffered with diammonium citrate or potassium phosphate. If an alum is also present potassium chromium alum is preferred. Reference is made to the product of both pure gold and bright lemon-yellow gold alloy deposits.