Adsorption and Corrosion Inhibition Effect of Schiff Base Ligands on Low Carbon Steel Corrosion in Hydrochloric Acid Solution

Abstract

In this study, the corrosion inhibition of low carbon steel in 2.0 mol L−1 HCl by N, N′-bis(salicylidene) benzidine (Schiff base A) and N,N´-bis(5-nitrosalicylidene) benzidine (Schiff base B) has been studied using chemical (weight loss) and electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy, EIS) measurements. Polarization curves reveal that the used compounds are mixed-type inhibitors. Results show that the inhibition efficiency increases when the inhibitor concentration increases and the inhibition efficiency follows the order: Schiff base B > Schiff base A. The obtained experimental data fitted Langmuir adsorption isotherm. Also, associated activation parameters (Ea, ΔH*, and ΔS*) and the thermodynamic adsorption parameters (Kads, Δ) were calculated and discussed. Quantum chemical calculations were performed to theoretically define the relationship between molecular structure and inhibition efficiency of Schiff base A and Schiff base B.