POST-TREATING ZINC SURFACES

摘要

A process for post-treating a chemical conversion coating on a Zn (alloy) surface comprises applying an aq. soln. contg. thiourea and a tannin or tannin acid to the coated Zn to improve the adhesion and corrosion resistance of a paint film which is subsequently applied. The passivating or sealing rinse is comparable to that obtd. with chromic acid and therefore reduces pollution.