Procedure for the production of semi-glossy and glossy electro-galvanic coatings using high current densities in a bath containing zinc salt of sulphuric acid and its composition

摘要

The inventors disclose a process for producing semi-bright to bright electrogalvanic coatings at high current densities, comprising electroplating a cathodic conductive substrate in a coating bath based on: a) a zinc sulfur-acid sa b) a low molecular weight polyoxyalkylene glycol based on 2 to about 4 carbon atom alkylene oxides; c) an aromatic sulfonate; and d) a conductivity enhancing salt. The process includes maintaining the coating composition at a pH from about 2 to about 5 and the current density on the substrate at from about 1,000 to about 3,700 ASF. The zinc sulfur-acid salt includes zinc sulfate or a zinc organosulfonate, and the conductivity enhancing salt, a potassium salt. In one embodiment, the aromatic sulfonate comprises a condensation product of an aromatic sulfonate and formaldehyde. The inventors also describes coating bath compositions.