Post treatment of zinc (alloy) e.g. galvanised surfaces - avoiding chromating, using phosphoric or phytic acids, tannin or hydrogen peroxide

摘要

Zinc(alloy) surfaces having been treated by chemical conversion are further treated with an aq. soln. contg. 0.02-5 g/l Ti ions and one or more of the following: phosphoric acid, phytic acid, tanninand H2O2 in a concn. of 0.1-10 g/l at a pH of 2-6. Used esp. on a galvanised steel surfaces to be subsequently painted. The post treatment soln. does not contain toxic chromium and can be used in place of chromating or phosphating in the presence of chromium. It thus avoids prodn. of toxic effluent without loss of corrosion resistance by the surface of the metal.