Abstract
The inhibitive effect of Damssisa and Hlfabar extracts on the corrosion of zinc in aqueous solutions of 0.5 M sodium hydroxide were investigated at 30 °C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization curves indicated that Damssisa and Hlfabar act as cathodic type inhibitors. Anodic polarization curves show active passive region. EIS measurements showed that the total resistance and consequently the inhibition efficiency increase with increasing concentration of Damssisa and Hlfabar indicating the inhibitive effect of these extracts on zinc corrosion. The inhibitive effect of the extract was assumed to occur via adsorption of active ingredients of the extracts on the metal surface. Theoretical fitting of different isotherms, Langumir, Florry-Huggins and the Kinetic-thermodynamic model were tested to clarify the nature of adsorption.