ELECTRODEPOSITION OF WHITE GOLD ALLOYS FOR DECORATIVE APPLICATIONS

摘要

Electrodeposited gold-tin and gold-silver-tin alloys are addressed as possible candidates for white gold alloys plating. An alternative, cyanide-free and acidic plating bath chemistry is considered using thiourea as ligand for Au(I), sulphuric or sulpharnic acid, and alloying metal cations. Process development is discussed with emphasis on the peculiarities of the cathodic electrochemical behaviour of the acid thiourea electrolyte. Electrodeposited coatings with bright and pleasant appearance can be obtained from the proposed baths, though limited in thickness, with composition in the range 14 to 22 carats. Thiourea based electrolytes are a possible alternative to cyanide and sulphite baths for Au alloys electrodeposition; further development is required for improvements in electrolyte stability and process control.