Corrosion inhibition of carbon steel in hydrochloric acid by furan derivatives

The efficiency of three furan derivatives (2-methylfuran, furfuryl alcohol and furfurylamine), as corrosion inhibitors for carbon steel in 1 M HCl, has been determined by gravimetric and electrochemical measurements. These compounds inhibit corrosion even at very low concentrations, and furfuryl alcohol is the best inhibitor. Polarization curves indicate that all compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of furan derivatives on the carbon steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. The structural and electronic properties of these inhibitors, obtained using AM1, PM3, MNDO and MINDO/3 semi-empirical self-consistence field methods, are correlated with their experimental efficiencies.