FREQUENCY DISPERSION OF THE INTERFACIAL IMPEDANCE AT MILD-STEEL CORROSION IN ACID-MEDIA IN THE PRESENCE OF BENZIMIDAZOLE DERIVATIVES

Measurements of the complex impedance of the interface between mild st eel and deaerated 1 M HCl solutions without and with the addition of d ifferent inhibitors, derivatives of benzimidazole, have been made in t he frequency range of (0.1-9.5) x 10(4) Hz. Adequate structure models of the interfaces as well as some data on the kinetics of the partial processes are offered. It is found that the double-layer capacity as w ell as the adsorption capacity can not be presented by a frequency ind ependent lumped element. The experimental data show a frequency distri bution and therefore a modeling element with frequency dispersion beha vior; a constant phase element has been used. At high inhibitor concen trations a second time constant is clearly observed in the impedance s pectra. It is most probably connected with the adsorption process. Two time constants determined by the charge transfer and the adsorption o f the inhibitor, respectively, can be readily outlined.