Electrochemical Determination of Corrosion Protection Properties of Chromated Zinc, Zinc Alloy and Cadmium Electroplated Coatings

摘要

Anodic galvanostatic investigations of chromated zinc, zinc alloy and cadmium electroplated coatings were carried out in three different corrosion media. It was established that the anodic potential of the chromated coatings passed through a maximum. The comparison between the anodic behaviour of the chromated coatings and their resistance in neutral salt spray showed that better corrosion-protective properties of the chromated films corresponded to the higher anodic potential maximum. This correlation provides the possibility to evaluate the corrosion resistance by measuring the anodic potential maximum on a defined small surface of the samples in a few minutes immediately after their drying. On the basis of the these investigations, a new electrochemical method for estimation of the corrosion-protective ability of the chromated coatings as well as a new type of apparatus were developed.