ES349930A1 - Semi-bright nickel plating - Google Patents

Abstract

Semi-bright nickel is electro-deposited on to a metal cathode, e.g. of ferrous metal, copper or copper alloy, zinc or copper-plated zinc, non- conductive or conductive articles coated as by electroless plating with silver or copper, from an aqueous acidic nickel bath including an aromatic aldehyde, i.e. a compound containing an aldehyde group and a benzene nucleus which may be substituted including substitution by a condensed ring but does not contain a sulphonic acid group, in combination with an aliphatic aldehyde. A compound containing the sulphohydrocarbyloxycoumarin ion may also be included in the bath. The substituents on the aromatic aldehyde may be ether, carboxy, carboxyester, hydroxy-containing groups, halogens or hydrocarbon groups such as alkyl, alkenyl, cycloalkyl, aryl, or mixed alkyl and aryl groups which may themselves be substituted by alkyl alkenyl, cycloalkyl, ether,. ester or halogen. Typical aromatic aldehydes are benzaldehyde, naphthaldehyde and their hydroxy and/or alkoxy derivatives, piperonal and its hydrocarbon, halogen, alkoxy and alkylcarboxy derivatives, the o-, m- and pdialdehydes of benzene and cinnamaldehyde, while the aliphatic aldehydes which preferably contain 1 to 10 carbon atoms are typically formaldehyde, paraformaldehyde, chloral or bromal or their hydrates, acetaldehyde propionaldehyde, butyraldehyde and hexylaldehyde. By employing high speed agitation of the bath, rapid deposition of nickel at a cathode current density of at least 10 amps/sq.dm. can be effected.