Inhibition mechanism and corrosion protection of mild steel in HCl using coumarin derivative: Gravimetrical and theoretical analysis

This research investigates the potential of 2-((2-oxo-2H-chromen-7-yl)oxy)acetic acid (CAE) to inhibit mild steel corrosion in 1 M hydrochloric acid using gravimetrical methods and scanning electron microscopy (SEM).The study explores the adsorption and inhibition mechanisms through weight loss analysis and density functional theory (DFT) calculations.The inhibitor exhibited a maximum efficacy of 87.5% at a concentration of 0.5 mM after a 10-hour immersion period at 303 K. Experiments conducted at different immersion times (5, 10, 24, and 48 hours) revealed 10 hours to be the most effective duration for the chosen inhibitor concentrations (0.1-1.0 mM) at 303 K. Inhibition efficiency increased proportionally with rising inhibitor concentration and remained stable beyond 10 hours up to 48 hours.The influence of temperature on the inhibition process was studied for varying inhibitor concentrations.Here again, 10 hours emerged as the optimal immersion time.The Langmuir adsorption isotherm model was successfully applied to understand the inhibitor's adsorption behavior on the mild steel surface.The variation in activation energy demonstrated that particular binding incidents existed between the inhibitor compounds and the cast mild steel surface.The DFT calculations made this interaction more vivid by providing more insight into them.Analysis found a slight difference in energy between HOMO and LUMO which proved the inhibitor effectiveness.The relevant data of the experiments and calculations show a good correspondence, which proves the efficacy of CAE as a corrosion inhibitor for mild steel in HCl environment.