Yellow Chromate Conversion Coatings on Zinc: Chemical Composition and Kinetics
- 1 January 1978
- journal article
- research article
- Published by Taylor & Francis in Transactions of the IMF
- Vol. 56 (1) , 51-54
- https://doi.org/10.1080/00202967.1978.11870452
Abstract
By means of precipitation titrations and EDAX the yellow chromate conversion coating was shown to be a basic zinc chromate. The conversion coating is formed according to a dissolution-precipitation mechanism. The rate of zinc dissolution is determined by diffusion through the coating and by the zinc(II)concentration in solution. The chromating solution is enriched in zinc(II)ions, because dissolved zinc ions do not precipitate completely, which reduces the activity of the chromating bath. The activity of the chromating bath can be restored by adding the appropriate anion. The presence of sulphate ions in the chromating solution influences the kinetics and the composition of the chromate conversion coating.Keywords
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