COMPARISON BETWEEN ELECTROCHEMICAL IMPEDANCE AND SALT SPRAY TESTS IN EVALUATING THE BARRIER EFFECT OF EPOXY PAINTS

The aim of this work is to establish the reliability of an electrochemical test based on the electrochemical impedance measurements of metallic substrate/organic coating/aqueous electrolytes as a function of immersion time. Thus, naval steel/epoxy-bituminous or epoxy-enamel coats/3% NaCl solution systems were chosen in order to try out the test. The electrochemical results and those obtained from visual assessment using the ASTM standard D-610 were compared. The total agreement between the results of the electrochemical and visual tests allow to confirm that the described technique is highly encouraging, as it has proven that a fairly straightforward test (like electrochemical impedance) can, under certain circumstances, indicate whether an anticorrosive paint coating is able to satisfactorily protect, as well as to detect differences between the anticorrosive properties of commercially available products.