Experimental and theoretical study of corrosion inhibition effect of expired Mebeverine drug on copper in 1.0 M sulfuric acid solution

• Musa E. M. Babiker

Department of Chemistry, Faculty of Science, Al-Baha University, Al-Baha 65779, Saudi Arabia

Abstract: In this work, we studied the corrosion inhibition effect of copper metal in 1.0 M H2SO4 solution utilizing the expired Mebeverine drug for human uses, by weight loss technique, electrochemical impedance spectroscopy techniques (EIS), potentiodynamic polarization (PP) and computational methods. The study was done at different temperatures (25, 35, 45, and 55°C) for three hours for weight loss study, in the presence of the inhibitor and the absence of the inhibitor with different concentration. According to the density functional theory (DFT)/P3LYP/6-311G, a number of parameters were determined in this work, including the highest occupied molecular orbital E_HOMO, the lowest unoccupied molecular orbital E_LUMO, energy gap (ΔE), dipole moment (μ), hardness (η), softness (S), electronegativity (χ), and electrons transferred fraction (ΔN). The adsorption of the Mebeverine drug on the copper surface followed Langmuir’s adsorption model. The adsorption of the Mebeverine drug on the copper is a physical adsorption type. The results showed that with the increment of the inhibitor concentration, there was an improvement of the inhibition efficiency, and the inhibition efficiency decreases with the rise in the temperature. The inhibition efficiency reached a value of 93.51% at 500 ppm of the inhibitor at 25°C and decreased to a value of 82.41% as the temperature increased to 55°C. Potentiodynamic Polarization (PP), and electrochemical impedance spectroscopy (EIS) results were in good agreement with the results of the weight loss (WL) method. Potentiodynamic polarization indicates a combined-type inhibition strategy, where the compound inhibits both anodic and cathodic reactions. Thermodynamic functions of adsorption and activation were determined and explained. The computational results carried out on the inhibitor agree with the experimental one. The employed techniques explain efficiencies in perfect correspondence, demonstrating the validity of these methods. The density functional theory (DFT) results indicated that the expired drug bound to the copper surface through the lone pair of electrons of the heteroatoms as well as the π-electrons of the two benzene ring.

Keywords: expired Mebeverine, copper, corrosion inhibition, H2SO4, DFT

Int. J. Corros. Scale Inhib., 2026, 15, no. 2, 88-112
doi: 10.17675/2305-6894-2026-15-2-6

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