Improvements in or relating to the electro-deposition of nickel

853,967. Levelled nickel electrodeposits. WILMOT-BREEDEN Ltd. Feb. 7, 1958 [Feb. 21, 1957], No. 5828/57. Class 41 Level nickel electrodeposits are produced by the addition to an acid aqueous nickel plating bath of a small dissolved proportion of one of the 6-sulphamido, 6-acetamido, 6-nitro, or 6-amino derivatives of coumarin, or of hydrocoumarin sulphonic or a salt thereof e.g. the sodium or potassium salt. The upper concentration given for the first three compounds is saturation and for the remaining compounds is 2À5 gms/litre. The nickel baths may be sulphate, chloride, or Watts type. 6-sulphamido and 6-acetamido coumarin give bright ductile deposits, the former compound having less good levelling properties and the latter a narrower bright plating range, 6-nitro- and 6-amino-coumarin give bright deposits which tend to crazing, while hydrocoumarin sulphonates give ductile semi-bright deposits. Any degradation products of the additives are removable by circulating the electrolyte by means of a pump through an external charcoal-loaded filter. The Provisional Specification refers also to the use of 6-hydroxycoumarin as a nickel plating bath additive. Specifications 622,671 and 622761 are referred to.