Experimental and computational chemistry studies of two imidazole-based compounds as corrosion inhibitors for mild steel in HCl solution

Abstract

Two imidazole-based corrosion inhibitors, namely thiazole-4-carboxylic acid (TCA) and 2-methyl-1,3-thiazole-4-carboxylic acid (MTCA), were synthesized and their corrosion inhibition performance on mild steel in 0.1mol·L−1 HCl solution at 25°C was investigated using electrochemical measurements. Corrosion inhibition efficiency increased with increasing inhibitor concentration in solution and at a concentration of 150ppm, both MTCA and TCA exhibited similar corrosion inhibition efficiencies of ~90%. Adsorption of both inhibitors on steel followed the Langmuir adsorption isotherm. Theoretical quantum chemical calculation and Monte Carlo simulation were employed to determine the most stable configuration, the adsorption sites, and the interaction energies of TCA and MTCA on the steel surface. The simulation results demonstrated that the competitive adsorption of inhibitors and water molecules, proton, and chloride ions has a large impact on the adsorption configuration of inhibitors.