Imidazole-fe interaction in an aqueous chloride medium: effect of cathodic reduction of the native oxide.

The effect of the reduction of the native surface oxide of Fe on the binding of imidazole (as a corrosion inhibitor) with Fe in an aqueous brine solution has been addressed here. The surface interactions and corrosion inhibition efficiency were studied using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). It was shown that imidazole dissolved in brine bonds with the unreduced iron oxide surface via pyrrole-type nitrogen. However, surface interactions with Fe occur via both pyridine-type and pyrrole-type nitrogen atoms when imidazole is added to brine containing a cathodically reduced iron surface. The packing density of imidazole is found to be higher in the latter case with a corresponding increase in the corrosion inhibition efficiency.