Browsing by Author "Chandrabhan Verma"

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5-Substituted 1H-tetrazoles as effective corrosion inhibitors for mild steel in 1 M hydrochloric acid
(Taylor and Francis Ltd., 2016) Chandrabhan Verma; M.A. Quraishi; A. Singh
The corrosion inhibition efficiency of (E)-3-phenyl-2-(1H-tetrazole-5-yl)acrylonitrile (PTA), (E)-3-(4-nitrophenyl)-2-(1H-tetrazole-5-yl)acrylonitrile (NTA), and (E)-3-(4-hydroxyphenyl)-2-(1H-tetrazole-5-yl)acrylonitrile (HTA) on mild steel in 1 M HCl was tested using experimental and theoretical methods. The results show that the inhibition efficiency increases with the increasing concentration, and maximum values were obtained at a 40 mg L−1 concentration. The inhibition efficiency of the studied inhibitors follows the order HTA (98.69%) > NTA (96.60%) > PTA (93.99%). Polarization studies suggest that the tetrazoles behave as cathodic inhibitors. The adsorption of the tetrazoles on the mild steel surface obeys the Langmuir adsorption isotherm. In the present study, the values of the free energy of adsorption ((Formula presented.)) vary from 34.92 to 39.71 kJ mol−1. The adsorption of the tetrazoles on the mild steel surface is supported by SEM, EDX and AFM studies. Quantum chemical calculations provide good support to the experimental results. © 2015 The Authors.
Synthesis, characterization and corrosion inhibition potential of two novel Schiff bases on mild steel in acidic medium
(Royal Society of Chemistry, 2017) Archana Pandey; B. Singh; Chandrabhan Verma; Eno E. Ebenso
The present study deals with the synthesis of two novel Schiff bases (SBs) namely; 5-((4-chloro-3-nitrophenylimino)methyl)-2-methoxyphenol (SB-1) and 2-(4-hydroxy-3-methoxybenzylidineamino)-4-nitrophenol (SB-2) using a solid-liquid phase equilibrium diagram and their characterization via1H and 13C NMR, FT-IR and UV-vis spectral analyses. Differential scanning calorimetric (DSC) thermographs were also obtained to further support the synthesis and identify the melting temperatures of SB-1 and SB-2. The XRD technique was employed to study the atomic packing, crystal structure and space group of the grown crystals of SB-1. Results showed that powder X-ray diffraction patterns of both SBs are entirely different than those of their corresponding starting compounds. The inhibition properties of the investigated SBs were evaluated for mild steel corrosion in 1 M HCl using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and computational (DFT) methods. Electrochemical and DFT studies revealed that the tested SBs act as good inhibitors for acidic corrosion of mild steel and their efficiency increases (η%) on increasing their concentrations. Electrochemical results revealed that SB-1 and SB-2 showed maximum inhibition efficiencies of 95.58% and 96.80%, respectively, at a concentration as low as 0.327 mM. Results from a polarization study suggest that the studied SBs act as mixed type corrosion inhibitors with some cathodic predominance. The DFT based parameters such as EHOMO, ELUMO, ΔE, electronegativity (χ), hardness (η), softness (σ) and the fraction of electron transfer (ΔN) were calculated to corroborate the experimentally obtained results. Both experimental and DFT results were in good agreement. This journal is © The Royal Society of Chemistry.
Synthesis, characterization and corrosion inhibition properties of benzamide–2-chloro-4-nitrobenzoic acid and anthranilic acid–2-chloro-4-nitrobenzoic acid for mild steel corrosion in acidic medium
(Elsevier B.V., 2018) Archana Pandey; Chandrabhan Verma; B. Singh; Eno E. Ebenso
The present study deals with the synthesis of two new compounds namely, benzamide – 2-chloro-4-nitrobenzoic acid (BENCNBA) and anthranilic acid–2-chloro-4-nitrobenzoic acid (AACNBA) using solid phase reactions. The phase diagram studies revealed that formation of the investigated compounds occurs in 1:1 molar ratio. The synthesized compounds were characterized using several spectral techniques such as FT-IR, 1H and 13C NMR, UV–Vis, powder X-ray diffraction (PXRD). Single crystal XRD (SCXRD) study showed that both BENCNBA and AACNBA compounds crystallize in triclinic crystal system with P-1 space group. Further, the presence of intermolecular hydrogen bonding between the constituent components was also supported by single crystal X-ray diffraction (SCXRD) method. Heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions have also been computed using the enthalpy of fusion values derived from differential scanning calorimeter (DSC) study. The inhibition effect of BENCNBA and AACNBA on the mild steel corrosion in hydrochloric acid solution was tested using electrochemical methods. Electrochemical impedance spectroscopy (EIS) study revealed that both BENCNBA and AACNBA behaved as interface corrosion inhibitors and showed maximum inhibition efficiencies of 95.71% and 96.42%, respectively at 400 ppm (1.23 × 10−3 M) concentration. Potentiodynamic polarization (PDP) measurements suggested that BENCNBA and AACNBA acted as mixed type corrosion inhibitors. EIS and PDP results showed that BENCNBA and AACNBA act as efficient corrosion inhibitors for mild steel and their inhibition efficiencies enhances on increasing their concentrations. © 2017 Elsevier B.V.