The inhibiting effect of 5,6-Dibenzyloxyindole (DPI) on corrosion of carbon steel (CS) was investigated in hydrochloric acid (1.0 M) by electrochemical and weight loss studies. It was found that DPI inhibits both partial corrosion reactions. The corrosion protection mechanism is by formation of a surface-adsorbed DPI film. A maximum inhibition efficiency of 93.03 % was achieved in 1.0 M HCl. The adsorption of DPI onto the CS surface was described by the Langmuir adsorption isotherm. The corresponding standard Gibbs energy of adsorption was calculated to be −36.84 kJ mol−1. Monte Carlo simulation approach was used to ascertain the correlation between inhibitive effect and molecular structure. Both the experimental and theoretical studies agree well in this regard and confirm that DPI is having a better interaction with the metal surface in 1.0 M HCl. The adsorption behaviors of this molecule on the steel surface have been studied using Monte Carlo method.
Keywords: Corrosion inhibition, Mild steel, 5,6-Dibenzyloxyindole, Monte Carlo simulation, Hydrochloric acid