Electroplating of chromium coatings from Cr(III)-based electrolytes containing water soluble polymer

Abstract

The effect of certain water-soluble synthetic polymers on the current efficiency, the kinetics of partial cathodic reactions, and certain properties of coatings at the chrome plating from sulfate-formate baths based on Cr(III) salts is studied. A polymeric additive of the nonionogenic type N1 (3 × 10 6 g/mol) is proposed, which favors the deposition of chromium coatings that have good adhesion to the surface, do not crack, and have a thickness of several tens micrometers. It is found that the polymers have an accelerating effect on the aggregation of the particles of the chromium-hydroxide sol formed in the near-electrode layer, which, apparently, improves the deposit quality and enhances the current efficiency. It is shown that the resulting amorphous-crystalline chromium deposits are sufficiently hard and exhibit good protectiven ability at the anodic dissolution in aggressive media.