EIS study of the corrosion behaviour of zinc-based coatings on steel in quiescent 3% NaCl solution. Part 2: coatings covered with an inhibitor-containing lacquer

An EIS study has been made of the behaviour of several lacquered and inhibited zinc-based coatings on steel exposed to a 3% NaCl solution in quiescent conditions. Under the hypothesis that the HF-LF arc supplied the Rt value of the corrosion reaction, the possibility of obtaining quantitative information about the effect of the lacquer film and the inhibitor on the progress of attack has been demonstrated. Different values of the constant B in the Stern-Geary equation must be used depending on the specific metallic coating tested. The relatively high interfacial capacitance values of the lacquered coating suggest a highly defective lacquer film which leave a considerable fraction of the surface of the metallic substrate exposed to the corrosive medium. © 2004 Elsevier Ltd. All rights reserved.