ELECTROCHEMICAL DETERMINATION OF CORROSION PROTECTION PROPERTIES OF CHROMATED ZINC, ZINC ALLOY AND CADMIUM ELECTROPLATED COATINGS

Anodic galvanostatic investigations of chromated zinc, zinc alloy and cadmium electroplated coatings were carried out in three different cor rosion media. It was established that the anodic potential of the chro mated coatings passed through a maximum. The comparison between the an odic behaviour of the chromated coatings and their resistance in neutr al salt spray showed that better corrosion-protective properties of th e chromated films corresponded to the higher anodic potential maximum. This correlation provides the possibility to evaluate the corrosion r esistance by measuring the anodic potential maximum on a defined small surface of the samples in a few minutes immediately after their dryin g. On the basis of the these investigations, a new electrochemical met hod for estimation of the corrosion-protective ability of the chromate d coatings as well as a new type of apparatus were developed.