Metal coatings for metal workpieces - obtd. by combined chemical and mechanical process in bath contg. metal powder, reaction mixt., activator, and inert impact bodies

摘要

The workpieces are immersed and agitated in an aq. acid bath with a pH adjusted to 1-2, where the bath contains solid inert bodies subjecting the workpieces to mechanical impact. An activator is added to the bath, and then the powdered metal which will form the coating, plus a reaction mixt.. The activator consists of an ethoxylated nonyl-phenyl-polyglycolether (I); and metal ions, esp. Cu and/or Sn ions, are added to the reaction mixt.. The reaction mixt. pref. contains hydrazine dichloride and/or hydrazine sulphate, and/or FeSO4, plus SnII - and/or SbII - cpds. forming a spongy layer of Sn or Sb on the particles of metal powder, i.e. the coating, which is esp. Zn, Sn, Cd, Ag, Au, or their alloys. As compared with electroplating, the invention does not cause hydrogen embrittlement.