GB1198527A - Improvements in Electrodeposition of Gold and Gold Alloys - Google Patents

Abstract

1,198,527. Electro-depositing gold and gold alloys. F.I. NOBEL and B.D. OSTROW. Aug.29, 1967, No.39554/67. Heading C7B. Gold or gold-base alloy is electro-deposited from an aqueous solution of at least one soluble gold cyanide salt in which there is dissolved an organo-phosphorus compound which does not contain in the molecule any straight - or branchedchain acyclic or cyclic aliphatic hydrocarbon residue which is linked directly to a phosphorus atom and which contains more than five carbon atoms. The organo-phosphorus may be a non- chelating agent, e.g. benzene phosphoric acid, benzene phosphinic acid, ethyl acid phosphate- C 2 H 5 O-PO(OH) 2 or diethyl phosphite; or may be a chelating agent, e.g. having the formula:- wherein R is an alkylidene radical, R<SP>1</SP> is hydrogen or an alkyl radical and n is an integer from 1 to 3, the radicals containing 5 or less carbon atoms, e.g. amino-tri (methy phosphonic acid), aminotri (ethylidene phosphonic acid), or amino-tri (isopropylidene phosphonic acid) or for instance 1-hydroxyethylidene-1, 1 diphosphonic acid; ethylenediaminetetra (methylphosphonic) acid; hexamethylene-diaminetetra (methylphosphonic) acid, or hexamethyl phosphonic triamide. The organo-phosphorus compound may be a salt of lithium, sodium or potassium or an ammonium or amine salt. The electrolyte may include a soluble citrate. The pH of the bath may be adjusted by addition of alkali metal hydroxide, e.g. potassium hydroxide, or phosphoric acid. To deposit gold base alloys, the plating bath may contain alloying metals such nickel, cobalt, iron, zinc and copper in the form of water soluble salts, e.g. the bath may contain nickel sulphate, nickel tartrate, cobalt sulphate or cobalt gluconate. Gold plate may be deposited on a brass base.