Abstract: It is an object of the present invention to provide an electroless gold plating solution capable of directly subjecting a plated coating film made of an underlying metal such as nickel or palladium to gold plate processing, of forming a thick gold plated coating film having a thickness of 0.1 ?m or more, of forming a uniform gold plated coating film, and of safely performing plating work. The present invention relates to an electroless gold plating solution comprising: a water-soluble gold compound; and hexahydro-2,4,6-trimethyl-1,3,5-triazine or hexamethylenetetramine. Preferably, the electroless gold plating solution comprises 0.1 to 100 g/L of hexahydro-2,4,6-trimethyl-1,3,5-triazine or hexamethylenetetramine.

Abstract: It is an object of the present invention to provide an electroless gold plating solution capable of directly subjecting a plated coating film made of an underlying metal such as nickel or palladium to gold plate processing, of forming a thick gold plated coating film having a thickness of 0.1 ?m or more, of forming a uniform gold plated coating film, and of safely performing plating work. The present invention relates to an electroless gold plating solution comprising: a water-soluble gold compound; and hexahydro-2,4,6-trimethyl-1,3,5-triazine or hexamethylenetetramine. Preferably, the electroless gold plating solution comprises 0.1 to 100 g/L of hexahydro-2,4,6-trimethyl-1,3,5-triazine or hexamethylenetetramine.

Abstract: An object is to provide practical silver plating technique, high-speed silver plating technique and silver strike plating technique which have, respectively, substantially the same performance as cyanide baths without use of any toxic cyanide. A hydantoin compound of the following general formula is contained as a complex-forming agent ##STR1## [wherein R.sub.1, R.sub.3 and R.sub.5 independently represent hydrogen, an alkyl group having 1-5 carbon atoms, an aryl group or an alcohol].