Mild steel corrosion inhibition comparison between indole-5-carboxylic acid and benzofuran-5-carboxylic acid: An integrated experimental and theoretical study

Abstract

Corrosion inhibition capabilities of Indole-5-carboxylic acid (IC) and Benzofuran-5-carboxylic acid (BC) on mild steel have been comprehensively investigated using various techniques, including Potentiodynamic Polarization Measurement (PPM), electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SEM). The results from polarization tests demonstrated that both IC and BC effectively reduced the corrosion current densities of both cathodic and anodic reactions occurring on the metal surface. Through EIS analysis, it was observed that the inhibitory efficacy of IC and BC increased with higher inhibitor concentrations. At a temperature of 30°C, the solution containing 10−2M IC and 10−2M BC exhibited the maximum inhibitory efficiency, with IC achieving 92.19% and BC achieving 75.00%. The adsorption behavior of the inhibitors was found to follow the Langmuir isotherm, suggesting a monolayer adsorption process. Additionally, quantum chemical calculations were carried out to assess the molecular parameters of the inhibitors thoroughly. These calculations consistently indicated that IC exhibited superior inhibitory properties compared to BC. Furthermore, molecular dynamics simulations were employed to gain insights into the optimal adsorption configuration of the inhibitors on the Fe(110) surface. The results revealed that IC possessed a higher binding energy with the Fe(110) surface, confirming its superior ability to inhibit steel corrosion compared to BC.