Procédé de préparation d'un dépôt brillant de nickel

Nickel plating baths are improved by adding a N-cyano sulphonamide of general formula in which Ra is (1) an aliphatic radical, (2) an aromatic radical or a substituted derivative thereof with a alkyl sulpho-, halo-, or acetamido group, or (3) a heterocyclic group; M is hydrogen, alkali metal, Mg, Co, Ni; and n is 1 to 3. Examples are, benzene-N-cyanosulphonamide, diphenyl sulphone-3:3'-di(N-cyano sulphonamide); RA may also be tri-chloro-methyl-, or 2-thiophene-. These are brightening agents to which may also be added levelling agents, especially acetylenic compounds and sulpho-oxygen compounds. For example, butyne diols, hydroxyethoxy butyne, olefinic glycols, nitriles, cyanamide, coumarin and quinoline compounds. A range of acetylenic compounds are described including a - a ' di-substituted compounds and polyoxyacetylenic compounds of general structure, (II) H-(OCH2CH2)x-O-CH2-C­C-CH2 -O-(CH2-CH2-O)y-H The sulpho-oxygen compounds include sulphonic and sulphinic acids, and their amides and imides or salts thereof with alkali metals, Ni, Co, or Mg. Nickel salts used in plating bath include sulphamate and fluoborate, which form a stress-free Ni plate.