Mild steel corrosion inhibition by nicotinamide as a green inhibitor: An electrochemical, thermodynamic and theoretical insight

• N. Dheer¹, A.K. Kalra², D. Singh³, S.K. Ujjain⁴, P. Ahuja⁴, R. Kumar⁵, P. Singh⁶, N.K. Johar⁷, M.R. Singh⁸ and R. Kanojia⁹

¹ Acharya Narendra Dev College, University of Delhi, Delhi, 110019, India
² SGTB Khalsa College, University of Delhi, Delhi, 110007, India
³ Daulat Ram College, University of Delhi, Delhi, 110007, India
⁴ Centre for Advanced Sensor Technology and Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore Country, Baltimore, 21250, MD, USA
⁵ Indo French Centre for the Promotion of Advanced Research, Lodhi Road, New Delhi, 110003, India
⁶ Atma Ram Sanatan Dharma College, University of Delhi, Delhi, 110021, India 7Maharaja Agrasen Institute of Technology, Delhi, India
⁷ Maharaja Agrasen Institute of Technology, Delhi, India
⁸ Kirori Mal College, University of Delhi, Delhi, 110007, India
⁹ Shivaji College, University of Delhi, Delhi, 110027, India

Abstract: The nature of inhibition, mechanism of adsorption and effect of concentration of nicotinamide (NCA) on corrosion of mild steel (MS) in 0.5 M H₂SO₄ were evaluated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods. Tafel plot reveals that NCA inhibits corrosion of mild steel and it acts as a mixed-typed inhibitor in acidic medium. The inhibition efficiency of NCA depends upon its concentration as well as temperature and it increases on increasing both concentration and temperature. The inhibition efficiency attained was 92.7% at 10^–1 M at 328 K while it was 77.6% at 10^–1 M at 298 K. The adsorption of NCA onto MS surface facilitates corrosion inhibition and the mechanism follows El-Awady adsorption isotherm model. The values of ΔG⁰_ads, ΔH⁰_ads and ΔS⁰_ads indicate the involvement of chemisorption in the adsorption of inhibitor. The increase of charge transfer resistance from 2.404 Ω·cm² in H₂SO₄ to 26.47 Ω·cm² and decrease in electrical double layer capacitance from 55.62·10^–4 F·cm^–2 in H₂SO₄ to 7.45·10^–4 F·cm^–2 in the presence of 10^–1 M NCA in EIS study signifies the mitigation of corrosion of MS. The scanning electron microscopy (SEM) confirmed the adsorption of NCA on MS and the development of the protective layer/film that leads to the corrosion inhibition. The mechanism of inhibition through the adsorption of NCA was also ascertained by quantum chemical calculation & density functional theory (DFT) studies. All the experimental and theoretical findings reveal that Nicotinamide is an efficient green inhibitor.

Keywords: inhibition, Tafel curve, density function theory, EIS, green inhibitor

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 1645-1667
doi: 10.17675/2305-6894-2023-12-4-13

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