GOLD-COBALT-INDIUM ALLOY PLATING BATH

PURPOSE:To obtain plating having specular gloss and a bright color tone by adding a citrate and a phosphate to the titled plating bath in combination with sodium ethylenediaminetetraacetate and butyne diol. CONSTITUTION:Sodium ethylenediaminetetraacetate and butyne diol are added to a plating soln. contg. Au, Co and In in the form of metallic salts so as to make the color tone of the resulting plating bright. A citrate and/or a phosphate having pH adjusting and buffing functions is further added to the plating soln. When the plating soln. is used, plating having a bright color tone and specular gloss which are not attained by conventional Au-Co, Au-In or Au-Co-In plating is obtd. Even through the plating bath is not controlled under strictly regulated conditions, high quality plating is obtd.