The paper investigates the corrosion inhibition property of the Bear Branch (Heracleum sphondylium) extract for copper in acid HNO3 solution. Potentiodynamic polarization and chronoamperometry techniques were used in this study in order to evaluate the inhibition efficiency of the proposed corrosion inhibitor in the mentioned solution. The Tafel plot method employed to determine value of the the corrosion current icorr as well as the corrosion rate. For a better simulation of the adsorption process of the extract on the metal surface, an equivalent circuit (EEC) has been modelled by using the data provided from the electrochemical impedance spectroscopy measurements. The possible interactions between the organic natural compounds molecules present in the extract of Heracleum sphondylium, have been evaluated by means of quantum chemical calculations and molecular modelling
