Electrolyte for gold plating - contg. gold sulphite-edta complex and alkali EDTA salts

摘要

Electrolyte for gold plating comprises (g/l) hexa-potassium-mu-EDTA-bis (gold (I) sulphite) (A) 10.5-210; alkali metal EDTA salt, 17.8-140 and the balance distilled water. Opt. it also contains 0.01-15 g/l EDTA-M-bis(2-amino-ethylammonium) complex (B) (M is cupric or Cd). The compsn. is made by reacting, in a single step at 80-90 deg.C, 12.6-250 g/l aurichloric acid; 39-1000 g/l alkali metal EDTA salts- 6-190 g/l alkali sulphite; 32-800 g/l KOH and 6.6-132 g/l NH4Cl. The ppte. (alkali metal chlorides and sulphates) is filtered off, leaving the electrolyte as filtrate. The electrolyte is useful in electronics, jewellery, radio technology and watch making. Compared with known (A)-based electrolytes, this soln. contains no K2HPO4 or K2SO4 impurities and has a higher (A) concn. It is easier to make and use (specifically practically no mechanical losses of gold) and can be stored at 25 deg.C for over 2 years. The addn. of (B) improves the current yield and gives a harder coating.