Weight loss, electrochemical measurements and DFT studies on corrosion inhibition by 7-mercapto-4-methylcoumarin

Abstract

Corrosion becomes a severe problem in several sectors due to its various effects. The present work focusing for corrosion inhibition efficiency of mild steel in 1 M HCl using 7-mercapto-4-methylcoumarin (MMC) through experimental and theoretical methods. Thus, the key goal is to understand to what extents MMC is efficient in avoiding corrosion in various situations. With this end in view, electrochemical impedance spectroscopy (EIS), dynamic polarization (DP) test and weight loss measurements were carried out. The outcomes showed the fact that corrosion mitigation efficiency was directly proportional to the concentration MMC but it was negatively proportional to temperature. The highest inhibition efficiency, up to the 95.8 %, was demonstrated at an inhibitor concentration of 0.5 mM. Based on Langmuir adsorption isotherm the wear properties of the mild steel indicated a mixed passive nature during MMC interactions. Additionally, quantum chemical calculations, including density functional theory (DFT), were achieved to determine the MMC molecular structure and its inhibition efficiency relationships. Key parameters such as the energy gap (Egap), EHOMO, ELUMO, hardness (η), softness, electronegativity (χ), and electron fraction transitions (ΔN) were also determine. The results from these computations were confirmed with the experimental results, confirming the mixed inhibition characteristics of MMC. The variation in activation energy in the presence of tested inhibitor further validated its effective as a corrosion inhibitor, with comprehensive insights into its potential industrial usages.