Investigating the corrosion inhibition properties of a Schiff base on mild steel in HCl solution: experimental and theoretical insights

• S.M.N. Ahmed¹, A.Y.I. Rubaye², S.A. Nawi³, A.H.M. Al-Musawi⁴, F.F. Sayyid¹, A.M. Mustafa¹, M.M. Hanoon¹, L. Shaker⁵, A. Al-Amiery^5,6, S.B. Al-Baghdadi⁷, T.S. Gaaz⁸ and A.A.H. Kadhum⁹

¹ Department of Production Engineering and Metallurgical, University of Technology, P.O. Box: 10001, Baghdad, Iraq
² Chemical and Petrochemical Techniques engineering Department, Basra Engineering Technical College, Southern Technical University, P.O. Box: 61004, Basra, Iraq
³ Departmrnt of Material, Engineering, College of Engineering- University of Diyala, P.O. Box: 32001, Diyala, Iraq
⁴ Baghdad oil Trining institute, Ministry of oil, , P.O. Box: 10001, Baghdad, Iraq
⁵ Engineering Technical College, Al-Ayen Iraqi University, AUIQ, An Nasiriyah, Dhi Qar, Iraq
⁶ Department of Chemical and Process Engineering, Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia, P.O. Box: 43600, Bangi, Selangor, Malaysia
⁷ Energy and Renewable Energies Technology Center, University of Technology, Iraq, P.O. Box: 10001, Baghdad, Iraq
⁸ Air Conditioning and Refrigeration Techniques Engineering Department, College of Engineering and Technologies, Al-Mustaqbal University, 51015 Babylon, Iraq
⁹ Faculty of Medicine, University of Al-Ameed, P.O. Box: 56001, Karbala, Iraq

Abstract: This research investigates the corrosion inhibition efficacy of 1-mesitylethanone thiosemicarbazone (MTSC), a Schiff base, on mild steel in HCl solution. The study employs weight loss assessment to analyze the corrosion inhibition properties, focusing on the influence of various MTSC concentrations during immersion periods at 303 K. The immersion times considered are 1, 5, 10, 24 and 48 hours. Additionally, the effect of temperature variation (303, 313, 323, and 333 K) on the inhibition efficiency of MTSC is examined. The experimental results reveal an optimal inhibitor concentration of 0.5 mM and an immersion time of 5 hours, where MTSC demonstrates an impressive maximum inhibition efficiency of 93.7%. Furthermore, the CR decreases from 6.62 mg·cm^–2·h^–1 at 0 mM inhibitor concentration to 0.34 mg·cm^–2·h^–1 at the optimal concentration, highlighting a significant reduction in corrosion. The concentration-dependent nature of inhibition efficiency is established, with inhibition efficiencies of 75.4%, 83.6%, 89.1% and 92.3% observed at concentrations of 0.1, 0.2, 0.3 and 0.4 mM, respectively. An inverse relationship between inhibition efficiency and temperature is also observed, with inhibition efficiencies of 93.7%, 90.2%, 87.6% and 84.3% recorded at temperatures of 303, 313, 323 and 333 K, respectively. Furthermore, adsorption isotherm analysis indicates conformity to the Langmuir adsorption isotherm. The free energy of adsorption ΔG⁰_ads is calculated to be ‑33.16 kJ·mol^–1, providing insights into the adsorption process. In parallel, density functional theory is employed to unravel the inhibition mechanism. The theoretical studies were achieved in the form of the parameters of E_HOMO (Highest Occupied Molecular Orbital), E_LUMO (Lowest Unoccupied Molecular Orbital), (nucleophilic index), (electronegativity), (chemical potential), and ΔN (the number of electrons transferred). It was observed that the obtained theoretical results are in suitable agreement with the experimental findings. Hence, it provides a complete idea about the corrosion inhibition nature of MTSC.

Keywords: corrosion inhibitor, DFT, Langmuir adsorption isotherm, mild steel, HCl

Int. J. Corros. Scale Inhib., 2024, 13, no. 3, 1797-1816
doi: 10.17675/2305-6894-2024-13-3-26

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