Electrochemical, spectroscopic and theoretical studies for acid corrosion of zinc using glycogen
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ORIGINAL PAPER
Electrochemical, spectroscopic and theoretical studies for acid corrosion of zinc using glycogen Mikitha Pais1 · Padmalatha Rao1 Received: 30 May 2020 / Accepted: 13 October 2020 © The Author(s) 2020
Abstract The objective of the work is to introduce and establish anticorrosion capabilities of a novel biopolymer glycogen (GLY) against sulfamic acid ( NH2SO3H) induced corrosion of zinc. The corrosion and inhibition studies were done by electrochemical techniques such as potentiodynamic polarization (PDP) measurements and electrochemical impedance spectroscopy technique (EIS). Conditions were optimized to get maximum inhibition efficiency by varying the concentration of the inhibitor in the temperature range of 303–323 K. Activation and thermodynamic parameters were evaluated and discussed in detail. Suitable adsorption isotherm was proposed to fit the experimental results. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and atomic force microscopy (AFM) studies were performed before and after the addition of inhibitor. Adsorption of inhibitor was further confirmed by UV–Visible spectroscopy. Quantum chemical calculations were done to establish the correlation between the structure of the inhibitor and its inhibition efficiency. Energy of HOMO, LUMO, energy gap ∆E, dipole moment (µ) Mullikan charges were calculated. Different theoretical factor descriptors like the hardness (η), and softness (σ) electronegativity (χ), global electrophilicity (ω), nucleophilicity (ε) and fraction of electron transferred (ΔN) were calculated. Inhibition efficiency of glycogen increased with increase in its concentration and with temperature. Maximum efficiency of 72% could be achieved for the addition of 0.05 g L−1 of GLY at 323 K. Results were fitted into Langmuir adsorption iostherm. The surface of the metal turned visibly smoother in the presence of GLY. In addition the EDX studies showed increase in carbon content which re-affirmed the adsorption of GLY on the metal surface. The density functional theory (DFT) based theoretical studies supported the experimental observations. Keywords Glycogen · Corrosion inhibition · Electrochemical studies · surface morphology · Adsorption studies · Theoretical studies
Introduction Zinc is considered to be one of the important nonferrous metal due to its wide range of industrial applications (Alsaleh and Khalil 2014). Zinc undergoes moderate to severe corrosion in the pH above 12 and below 6. In between this pH range, corrosion rate is reported to be moderate (Mahida and Chaudhari 2012; Vashi and Desai 2012; Charitha and Rao Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11696-020-01391-z) contains supplementary material, which is available to authorized users. * Padmalatha Rao [email protected] 1
Department of Chemistry, Manipal Institute of Technology, MAHE, Manipal 576104, Karnataka, India
2018). Various industrial processes such as pickling, descaling etc. will expose the metal to acidic en
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