Effective inhibition of mild steel corrosion by 6-bromo-(2,4-dimethoxyphenyl)methylidene]imidazo [1,2-a]pyridine-2-carbohydrazide in 0.5 M HCl: Insights from experimental and computational study

• Published in: Journal of molecular structure Vol. 1232; p. 130074
• Main Authors: Vranda Shenoy, K, Venugopal, Pushyaraga P, Reena Kumari, P D, Chakraborty, Debashree
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2021
• Subjects: Corrosion inhibitor; DFT studies; Electrochemical study; Langmuir's adsorption isotherm; Mild steel; Langmuir's adsorption isotherm; Mild steel; DFT studies; Corrosion inhibitor; Electrochemical study
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2021.130074

•Anti-corrosion effect of DMPIP (imidazopyridine derivative) on mild steel in HCl was studied.•Electrochemical studies showed mixed inhibitory action of DMPIP and formation of protective film on metal.•Adsorption of protonated DMPIP on metal is mainly due to electrostatic interaction.•SEM and EDX showed presence of a protective film of DMPIP on mild steel surface.•DFT calculation supported experimental observations through molecular parameters. A new inhibitor, 6-bromo-(2,4-dimethoxyphenyl)methylidene]imidazo [1,2-a]pyridine-2-carbohydrazide (DMPIP) was evaluated as a corrosion inhibitor for Mild Steel (MS) in 0.5 M HCl solution at 303–323 K using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. Both the techniques confirmed an increase in inhibition efficiency with the concentration of DMPIP but decrease with temperature. The highest inhibitive action (96.7%) was registered at 303 K for 500 ppm of DMPIP concentration. Polarization study revealed mixed inhibition action by DMPIP. Nyquist plot obtained for MS using EIS technique showed two capacitive loops on addition of inhibitor to HCl solution confirmed the inhibitory action of DMPIP via adsorption at the metal/solution interface. The surface morphology analysis was carried out by SEM, EDX and FTIR techniques. The adsorption process was demonstrated using Langmuir's adsorption isotherm model. The thermodynamic parameters (∆Goads, ∆Hoads) indicated that the adsorption was spontaneous and done by physisorption. Further, quantum chemical studies using Density Functional Theory (DFT) elucidated that the formation of Fe-DMPIP complex presumably due to the interaction of protonated form of DMPIP with the empty d orbitals of the iron atom. [Display omitted]