Abstract
The anticorrosive properties of six non-toxic pigments have been compared with those of zinc chromate. Following incorporation in an epoxy-polyamide resin} the pigments were applied to cold rolled steel and galvanised steel substrates. The painted panels were exposed to total immersion in 0·5M NaCl solution. Coating deterioration was monitored by electrochemical impedance spectroscopy (EIS) complemented by visual evaluation and adhesion tests. Water permeability into the paints was monitored by a single frequency impedance method. A most probable equivalent circuit for the polymer coated metal system is proposed. Good correlation was observed between the delaminated area obtained by EIS measurements and that obtained by visual observations of the specimens after exposure. The performance of zinc phosphate on cold rolled steel in immersion tests was superior even to that of zinc chromate. All pigments except zinc chromate fared worse on galvanised steel than on cold rolled steet probably owing to poor wet adhesion.
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