A COMPOSITION FOR CONVERSION COATING A ZINCIFEROUS METAL SUBSTRATE, A METHOD FOR TREATING A ZINCIFEROUS METAL SUBSTRATE, A TREATED ZINCIFEROUS METAL SUBSTRATE AND ITS USE

摘要

A composition for conversion coating a zinciferous metal substrate is provided, which is an aqueous non-chrome solution and comprises the following components: (a) phosphoric acid, (b) complex fluoride of titanium, (c) vanadium ions source; the content of each component respectively is as follows: the concentration of vanadium ions (c) derived from vanadium ions source in the composition ranges from 1 g/L to 20 g/L, the molar ratio of vanadium ions (c) to phosphate ions (a) ranges from 1:4 to 1:2, the molar ratio of vanadium ions (c) to complex fluoride of titanium (b) ranges from 3:2 to 3:1. Also provided are a formulating composition useful for giving the above composition through dilution with water, a method for contacting the zinciferous metal substrate with the above composition to form a conversion coating, and a conversion treated zinciferous metal substrate obtained by the above method and its use. Additional cleaning is not required after conversion treating the surface of the zinciferous metal substrate using the above composition, in particular, a chromate passivation cleaning is not required; therefore, the step of conversion treating is easy and does not lead to environmental chromium pollution.