Experimental and theoretical investigations on the inhibition efficiency of N-(2,4-dihydroxytolueneylidene)-4-methylpyridin-2-amine for the corrosion of mild steel in hydrochloric acid

• Y.M. Abdulsahib¹, A.J.M. Eltmimi², S.A. Alhabeeb³, M.M. Hanoon¹, A.A. Al-Amiery^4,5, T. Allami⁵ and A.A.H. Kadhum⁵

¹ Production Engineering and Metallurgy, University of Technology, P.O. Box: 10001, Baghdad, Iraq
² Al-Esraa University College (EUC) P.O. Box: 10001, Baghdad, Iraq
³ College of engineering, University of Warith Al-Anbiyaa, Karbala, Iraq
⁴ Energy and renewable energies technology center, University of Technology, Baghdad, 10001 Iraq
⁵ Department of Chemical and Process Engineering, University Kebangsaan Malaysia (UKM), P.O. Box: 43000, Bangi, Selangor, Malaysia

Abstract: Low carbon steel is an important construction material utilized in various industries mostly for its outstanding mechanical characteristics and its rather low cost compared to other materials. The current investigation studies the ability of N-(2,4-dihydroxytolueneylidene)-4-methylpyridin-2-amine (N-MDA), a Schiff base, on low-carbon steel corrosion inhibition in 1 M HCl environment utilizing weight loss techniques under the effect of different methodological restrictions. Experimental findings showed that (N-MDA) is an efficient inhibitor and inhibitive efficacy increased with increasing N-MDA concentration; reaching the highest rate of 93.7% at a N-MDA concentration of 0.0005 M. The effect of temperature of N-(2,4-dihydroxytolueneylidene)-4-methylpyridin-2-amine on the corrosion of low carbon steel in 1 M HCl solution was also investigated by weight loss experiments at temperatures ranging from 303 to 333 K. The adsorption of the N-MDA molecules on the low-carbon steel surface followed the Langmuir isotherm model with the adsorption free energy (ΔG⁰_ads) of −38.9 kJ∙mol^–1. Density function theory (DFT) has been used to perform quantitative calculations to correlate the structural and electronic properties of the investigated N-MDA molecules with the evaluation of the inhibitory activity. Electronic factors such as the Highest Occupied Molecular Orbital (HOMO), the Lowest Unoccupied Molecular Orbital (LUMO), the energy gap (ΔE), hardness, softness and electronegativity were calculated and discussed. The conclusions reached from the weight loss measurements and quantum chemical calculations are in good agreement.

Keywords: weight loss, density function theory, low-carbon steel, corrosion inhibition

Int. J. Corros. Scale Inhib., 2021, 10, no. 3, 885-899
doi: 10.17675/2305-6894-2021-10-3-3

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