Investigation of the Corrosion Inhibition of Carbon Steel in Acidic Solutions by One Schiff Base: Experimental and Theoretical Studies

Abstract

Schiff base was synthesized and characterized, namely: 4-(1-(4-(dimethylamino)benzyl)-5-methyl-1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (L). The molecular chemical structure of L was determined using 1H NMR, FT-IR, UV-Vis spectroscopy, and elemental analysis. The performance and inhibition mechanism of compound L against the corrosion of carbon steel in 1 M HCl and 0.5 M H2SO4 were studied by the weight loss method and by electrochemical techniques (Tafel polarization and electrochemical impedance spectroscopy (EIS)). Outcome data obtained from these methods displayed that with increasing the concentration of compound L, its inhibition efficacy (η %) increases and reached 82.85% at 1 × 10–2 M, 25 °C using weight loss method. On the other hand, % η declined to 75.25% at the same concentration and at 55 °C. The polarization curves indicate that this compound behaves as mixed-type inhibitor. The adsorption of this compound was found to obey the Langmuir adsorption isotherm. The morphological appearance of the carbon steel surface of compound L using scanning electron microscopy (SEM) photos and atomic force microscopy (AFM) confirmed that compound L was adsorbed on carbon steel forming a film. The kinetic and thermodynamic parameters were calculated and discussed. Furthermore, the quantum chemical parameters were determined using the Density Functional Theory (DFT) method. This study confirms that there is agreement between experimental and theoretical results.