Innovative benzo[d]imidazole-oxadiazole derivative for corrosion inhibition of C38 steel in hydrochloric acid: experimental and theoretical insights

• L. Naciri¹, S. Jebbari², K. Bouiti¹, A. Barhoumi³, M. Omari⁴, I. Bouhouche¹, S. Lakhloufi¹, N. Labjar¹, H. Nasrellah⁵ and S.El Hajjaji⁶

¹ LS3MN2E, CERNE2D, ENSAM, Mohammed V University in Rabat, Rabat, Morocco
² Laboratory of Bio-organic Chemistry, Department of Chemistry, Faculty of Sciences, Chouaib Doukkali University, El Jadida, Morocco
³ Laboratory of Organic Bioorganic Chemistry and Environment, Faculty of Sciences, University Chouaib Doukkali, Morocco
⁴ Agro-industrial, Environmental and Ecological Processes Team, Faculty of Science and Techniques of Beni Mellal, Sultan Moulay Slimane University, Beni Mellal, Morocco
⁵ ESEF, Chouaib Doukkali University of El Jadida, Morocco
⁶ LS3MN2E, CERNE2D, Faculty of Sciences, Mohammed V University in Rabat, Rabat, Morocco

Abstract: In this work, a novel benzo[d]imidazole-oxadiazole derivative (OXDZ2) was synthesized and comprehensively evaluated as a corrosion inhibitor for C38 steel in 1 M hydrochloric acid, using a combination of advanced experimental and theoretical approaches. The structure and purity of OXDZ2 were confirmed by FTIR, ¹H and ¹³C NMR, and high-resolution mass spectrometry. Electrochemical measurements, including Tafel polarization and electrochemical impedance spectroscopy, demonstrated that the addition of OXDZ2 led to a substantial decrease in corrosion rate, achieving a maximum inhibition efficiency of 96.97% at the optimal concentration. This high efficiency was reflected by a significant reduction in corrosion current density and an increase in charge transfer resistance. Surface morphology analysis using scanning electron microscopy revealed the formation of a homogeneous and compact protective film on the steel surface in the presence of OXDZ2. Theoretical investigations, based on density functional theory calculations and molecular dynamics simulations, provided molecular-level insights into the adsorption behavior and interaction mechanisms of OXDZ2 on the Fe (110) surface. Quantum chemical descriptors – including HOMO-LUMO energies, energy gap, electronegativity, hardness, electrophilicity index, and fraction of electrons transferred – highlighted the electronic reactivity of the inhibitor and the donor-acceptor interactions with the metal. Adsorption studies confirmed that OXDZ2 follows the Langmuir isotherm, with thermodynamic parameters indicating that chemisorption is the dominant mechanism.

Keywords: corrosion inhibitors, benzo[d]imidazole-oxadiazole, hydrochloric acid, electrochemical impedance spectroscopy, density functional theory

Int. J. Corros. Scale Inhib., 2025, 14, no. 3, 1289-1322
doi: 10.17675/2305-6894-2025-14-3-15

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