Browsing by Author "Ramkumar, Sowmya"

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ANTI‐CORROSIVE PROPERTY OF BIOINSPIRED ENVIRONMENTAL BENIGN IMIDAZOLE AND ISOXAZOLINEHETEROCYCLICS: A CUMULATIVE STUDIES OF EXPERIMENTAL AND DFT METHODS
(Wiley Periodicals, Inc., Journal of Heterocyclic Chemistry, 2019-12-13) Ramkumar, Sowmya; D, Nalini; Mumtaz A Quraishi; Eno E Ebenso; Chandrabhan Verma
In the present study, four imidazoline (IDZ) and four isoxazolines (ISO) heterocyclics differing in the nature of methoxy (‐OCH3) and aromatic (phenyl and naphthyl) moieties are synthesized, characterized and evaluated as corrosion inhibitors for mild steel in acidic solution of 1 M HCl. Results showed that imidazoline based heterocyclic compounds are better corrosion inhibitors than isoxazoline based heterocyclics and both classes of compounds showed inhibition efficiency of more than 85% at 20 mgL−1 concentration. Results further showed that inhibitors containing methoxy, phenyl, and naphthyl moieties showed higher protection efficiency as compared to the inhibitors without these moieties. PDP Study revealed that investigated IDZs and ISOs acted as mixed type inhibitors and their adsorption on the metallic surface followed the Langmuir adsorption isotherm model.All the experimental results were corroboratedby density function theory (DFT) based quantum chemical calculations.Numerous DFT based indices calculated for neutral as well asprotonated forms of the IDZs and ISOs in order to get better insight aboutmetal-IDZs/ISOs interactions. Outcomes of the DFT analysis showed that protonated(cationic) form of the all the inhibitors are more strongly adsorbed onthe metallic surface as compared to their neutral form.
A COMBINED EXPERIMENTAL AND THEORETICAL INVESTIGATION ON PYRAZOLONE DERIVATIVE AS CORROSION INHIBITOR FOR MILD STEEL IN 0.5 M SULPHURIC ACID MEDIA
(Sociedade Portuguesa de Electroquímicals, PortugaliaeElectrochimicaActa, 2014-04-23) Nalini D; Kohilah K S; Ramkumar, Sowmya
The inhibition action of the Pyrazolone Derivative (PYR) on the corrosion of mild steel in 0.5 M sulphuric acid was investigated by weight loss, polarization, impedance and SEM. Results obtained revealed that PYR performed excellently as corrosion inhibitor with efficiency of 91% at 11 ppm at 298 K. Its adsorption on mild steel obeys Langmuir and Temkin isotherm. Polarization curves indicate that PYR behaves as mixed type. The value of ΔG°ads indicates the spontaneous physisorption of PYR. The SEM results confirm the presence of a protective surface layer over the mild steel surface. The reactivity of the compound was analysed through theoretical calculation.
CORRELATION BETWEEN INHIBITION EFFICIENCY AND CHEMICAL STRUCTURE OF NEW INDOLOIMIDAZOLINE ON THE CORROSION OF MILD STEEL IN MOLAR HCL WITH DFT EVIDENCES
(Oriental Scientific Publishing Company, 2015-03-27) Ramkumar, Sowmya; D, Nalini
The present work aims at the synthesis, characterization and study on the inhibitive effect ofindoloimidazoline derivative (DI) on mild steel in 1M HCl. Weight loss measurement and electrochemicalAC and DC corrosion monitoring techniques are performed at 308 K using mild steel specimensimmersed in 1M HCl in the presence and absence of DI. Polarisation curves indicated that DI acted asa mixed type inhibitor. The indoloimidazoline derivative having nitrogen atoms in its molecular structureare adsorbed on the metal surface through these active centres and that the extent of inhibition isdirectly related to the formation of the adsorption layer according to Langmuir isotherm model on themild steel surface which is sensitive function of the molecular structure. Quantum chemical calculationsperformed using DFT B3LYP 6-31G (d, p) basis set within the program Gaussian 09 showed theadsorption sites for DI on mild steel. Experimental and theoretical findings agreed well with each other.
CORROSION INHIBITION OF N80 STEEL IN 15% HCL BY PYRAZOLONE DERIVATIVES: ELECTROCHEMICAL, SURFACE AND QUANTUM CHEMICAL STUDIES
(Royal Society of Chemistry, RSC advances, 2016-02-04) K R, Ansari; M A, Quraishi; A, Singh; Ramkumar, Sowmya; I B, Obote
The corrosion protection of N80 steel in 15% HCl by two pyrazolone derivatives namely 2-(3-amino-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)(p-tolyl)methyl)malononitrile (PZ-1) and 2-((3-amino-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)(phenyl)methyl)malononitrile (PZ-2) has been investigated by using gravimetric, electrochemical and quantum chemical studies. The observed results reveal that PZ-1 is a better inhibitor than PZ-2. Tafel polarization showed that PZs are mixed type inhibitors but dominantly affect the cathodic reaction. Both inhibitors were found to obey the Langmuir adsorption isotherm. Scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) images support the protection of the N80 steel in the presence of the PZs. Quantum chemical study reveals that both inhibitors have a tendency to get protonated and this result supports the experimental observations.
MACROCYCLIC COMPOUNDS AS GREEN CORROSION INHIBITORS FOR ALUMINIUM: ELECTROCHEMICAL, SURFACE AND QUANTUM CHEMICAL STUDIES
(Russian Association of Corrosion Engineers, 2018-09-28) Ansari K R; Ramkumar, Sowmya; Chauhan D S; Salman M D; Nalini D; Srivastava V; Quraishi M A
In the present work, two macrocyclic compounds namely 5,6,11,12-tetramethyl-1,2,4,7,8,10-hexaazacyclododeca-4,6,10,12-tetraene-3 ,9-dithione (TMCD) and 5,6,11,12- tetraphenyl- 1,2,4,7,8,10-hexaazacyclododeca-4 ,6,10,12-tetraene-3 ,9-dithione (TMPD) have been synthesized and for the first time reported as inhibitors against the corrosion of aluminium in 1 M hydrochloric acid. The synthesized compounds were characterized using H-1 NMR and C-13 NMR. The corrosion inhibition behaviour of TMCD and TMPD was studied using gravimetric measurements, electrochemical impedance spectroscopy and potentiodynamic polarization studies. The surface analysis was carried out using AFM and SEM. Theoretical studies on the adsorption behaviour of inhibitor were carried out using the Density Functional Theory method. A detailed study of the effect of temperature and the influence of immersion time is presented using weight loss technique. Potentiodynamic polarization study proves that the corrosion inhibition efficiencies of TMCD and TMPD at 400 mg L–1 concentration are 97.30% and 89.71% respectively. Both the inhibitors behaved as mixed type but exhibit cathodic predominance. The results of EIS-Nyquist plots show inductive behavior at low frequency characteristic of the electrochemical behaviour of aluminium. The increase in polarization resistance with concentration suggests the adsorption and corrosion inhibition behaviour for both TMCD and TMPD. The AFM studies reveal a considerable decrease in surface roughness in the presence of inhibitors compared to blank sample and the SEM images show a highly smooth surface of the metal sample in the presence of inhibitors. The Fukui functions, global softness and Mulliken charges reveal that the sites for electrophilic attack are the hetero atoms. The frontier molecular orbital energies, the molecular orbital energy gap and the other quantumchemical parameters corroborated the experimental observations and suggested a better performance of TMCD compared to TMPD molecule.
STUDIES ON ADSORPTION AND CORROSION INHIBITIVE PROPERTIES OF QUINOLINE DERIVATIVES ON N80 STEEL IN 15% HYDROCHLORIC ACID
(Taylor & Francis Group, 2016-01-25) Ramkumar, Sowmya; D, Nalini; M A, Quraishi
This paper deals with the N80 steel corrosion protection study in 15% HClwhich was carried by three quinoline derivatives namely 3-acetyl-1-(4-methylbenzylideneamino)quinolin-2-one (AQ-1), 3-acetyl-1-(4 hydroxybenzylideneamino)quinolin-2-one (AQ-2), 3-acetyl-1-(3-nitrobenzylideneamino) quinolin-2(1H)-one(AQ-3) using gravimetric, electrochemical, and quantum chemical studies. Tafel polarizationshowed that AQs are mixed type inhibitors but dominantly affect cathodicreaction more. The observed results reveal that AQ-1 is the best inhibitor. All thethree inhibitors were found to obey the Langmuir adsorption isotherm. Scanningelectron microscopy (SEM) micrographs supports the protection of the N80 steel byAQs. Quantum chemical study reveals that the inhibitors have a tendency to getprotonated and this protonated form has greater tendency to get adsorbed onto theN80 steel surface.