Inhibition of Carbon Steel in Cooling Water Systems by Nicotinamide

Nicotinamide as organic inhibitor has anticorrosive properties and for this reason, was used for cooling water systems protection. The inhibition activity analysis of this new organic inhibitor was made by assuming that the mechanism of inhibition by organic molecules is chemisorptions and that the energetic of the corrosion process per se is unaffected by the addition of substituents on the parent compound. We presume that, this organic inhibitor, nicotinamide, inhibit corrosion of carbon steel by a protective mechanism, forming insoluble iron complexes and repairing the porous oxide layers. The methods employed were potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM) and metallurgical microscopy techniques. The addition of the organic inhibitors led in all the cases to inhibition of the corrosion process. The inhibition efficiency was high in all the studied cases. The corrosion parameters obtained from polarization curves and from EIS spectra are in good concordance and point out the inhibitory action of nicotinamide. The adsorptions of the organic compounds on the carbon steels surface obeyed Langmuir^’s isotherm. Further characterization using Fourier transform infrared spectroscopy (FT-IR) demonstrates the adsorption of organic inhibitors and the formation of corrosion products on the carbon steels surface. The inhibition process was attributed to the formation of the adsorbed film on the metal surface that protects the metal against corrosive agents. The EIS measurements have confirmed this protection and pointed out the formation of adsorption layers on the electrode surface.