Inhibition performance of 2,2´-terephthaloylbis(N-methylhydrazinecarbothioamide) for mild steel in HCl: Insights from experimental measurements and DFT calculations

• N. Betti¹, W.K. Al-Azzawi², H.F.S. Ahmad³, R.K. Al-Azzawi², L.M. Shaker⁴, A.A. Al-Amiery^4,5, Q.A. Jawad⁶ and A.A.H. Kadhum⁷

¹ Materials Engineering Department, University of Technology-Iraq, Baghdad 10001, Iraq 2Al-Farahidi University, Baghdad, 10001, Iraq
² Al-Farahidi University, Baghdad, 10001, Iraq
³ Department of Medical Instrumentation Engineering, Al‐Mansour University College, Baghdad, 10001 Iraq
⁴ Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
⁵ Energy and Renewable Energies Technology Centre, University of Technology, Baghdad 10001, Iraq
⁶ Electrical Engineering Department, University of Technology, Baghdad 10001, Iraq
⁷ University of Al-Ameed, Karbala, 56001, Iraq

Abstract: The aim of this work was to investigate the effect of corrosion inhibition by a novel synthesized thiosemicarbazide derivative, namely 2,2´-terephthaloylbis(N-methylhydrazinecarbothioamide) (TBM), for mild steel (MS) in 1 M hydrochloric acid solution. This compound was characterized by Nuclear magnetic resonance (¹H-NMR and ¹³C-NMR) and Fourier transform infrared (IR) techniques in addition to elementary micro-analysis (CHN). The corrosion inhibition effect was examined using weight loss measurements and density functional theory (DFT). The morphology of the MS surface was characterized by scanning electron microscopy (SEM) technique. The results show significant corrosion inhibition for mild steel with an efficiency of 97.1% at 5.0 mM as the optimum tested concentration. This study has demonstrated that this synthesized corrosion inhibitor (TBM) provides excellent corrosion protection of MS in the corrosive solution. Evaluation of the MS surface by scanning electron spectroscopy demonstrates that the TBM molecules were adsorbed on the surface of MS. The adsorption of TBM followed the Langmuir adsorption isotherm. DFT was used to determine the adsorption sites of TBM molecules. The energy of the highest occupied molecular orbital (E_HOMO) shows significant tendency to donate electrons to the d-orbital of iron atoms. The energy of the lowest unoccupied molecular orbital (E_LUMO) reveals a high tendency to accept electrons from iron atoms on the surface of MS.

Keywords: corrosion inhibitor, mild steel, Langmuir, weight loss, adsorption

Int. J. Corros. Scale Inhib., 2022, 11, no. 1, 245-256
doi: 10.17675/2305-6894-2022-11-1-13

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