The invention provides a bath that is operable at, or close to, pH 7 to deposit a coating of ruthenium on a substrate, e.g. the contacts of electrical switches, which does away with the need to provide a protective coating on the substrate prior to ruthenium plating. The bath consists essentially of (i) a compound or a complex that contains a nitrogen bridge linkage joining together two ruthenium atoms and (ii) an aqueous solution of oxalic acid or an oxalate.