| 摘要 |
Electroplating bath comprises an aq. acidic soln. contg. zinc and nickel ions, an electrolyte in the form of a soluble ammonium salt, and a polyoxyalkylated nonionic surfactant. Preferred anions for the Zn, Ni and NH4 salts are chloride, sulphate, fluoborate and acetate, the Zn alternatively being present as the oxide and the Ni alternatively being present as the sulphamate. The surfactant is pref. selected from alkoxylated alkyl phenols and naphthols, aliphatic monhydric alcohols, polyoxypropylene glycols, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, ethylene diamine, fatty acids, amides and esters. The bath is useful for forming corrosion resistant Zn-Ni alloy layers on high strength steel parts. The bath is free of Cd ions, cyanides and chelating agents, yet has high cathode efficiency and produces smooth adherent, ductile, level and fine-grained deposits over a wide range of plating conditions and cathode current density. The plated part shows lower hydrogen embrittlement and greater corrosion resistance than prior art Zn or Zn-Ni alloy coated parts. Additionally, the bath is very stable, is easy to control, has high conductivity and requires only simple waste treatment procedures. |
