Browsing by Author "D, Nalini"

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ANTI-CORROSIVE PROPERTY OF BIOINSPIRED ENVIRONMENTAL BENIGN IMIDAZOLE AND ISOXAZOLINE HETEROCYCLICS: A CUMULATIVE STUDIES OF EXPERIMENTAL AND DFT METHODS
(2020) Sowmya, Ramkumar; 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 corroborated by density function theory (DFT) based quantum chemical calculations. Numerous DFT based indices calculated for neutral as well as protonated forms of the IDZs and ISOs in order to get better insight about metal-IDZs/ISOs interactions. Outcomes of the DFT analysis showed that protonated (cationic) form of the all the inhibitors are more strongly adsorbed on the metallic surface as compared to their neutral form.
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.
COMPARISON OF CORROSION INHIBITION OF MILD STEEL IN ACID MEDIA BYIMIDAZOLINE DERIVATIVE SYNTHESIZED BY CONVENTIONAL AND MICROWAVE SYNTHESIS
(Vivekanandha Arts and Science College for Women, 2020-02-07) SowmyaRamkumar; S, Rajakumari; D, Nalini
Acid solutions are widely used in industry, some important field of application being acid pickling, industrial cleaning, acid descaling, petrochemical processes etc. The majority of the corrosion inhibitors employed during production of steel form thin barrier layers between the steel surface and the corroding fluid. It was found that the formation of donor-acceptor surface complex between free or π-electrons of an organic inhibitor and vacant d-orbital of a metal is responsible for the inhibition of corrosion process. In the present study, Imidazoline derivative synthesized by conventional and microwave method is investigated for its anti-corrosion potential against mild steel in 1M HCl and 0.5M H2SO4 solution using electrochemical impedance spectroscopy, Potentiodyamic polarization and quantum chemical studies. Synthesized inhibitor is characterised by FTIR Spectra, DLS and SEM. The inhibition efficiency was evaluated at different concentrations of the inhibitor. The present investigation is carried out to find whether the greater inhibition efficiency for inhibitor synthesized by microwave method than conventional method. Electrochemical impedance spectroscopy: Nyquist plots for mild steel in 1M HCl and 0.5M H2SO4 with and without inhibitor results in increase in Rct values and decrease in Cdl shows the formation of the protective film of the inhibitor on the metal increases the efficiency of the inhibitor. The maximum inhibition efficiency of the inhibitor 98% and 79% at 20 ppm in HCl and H2SO4 synthesized by microwave method and by conventional method it shows the maximum efficiency of 89% and 70% respectively. From the Polarisation Measurements the Tafel constants obtained from the potentiodynamic polarisation curves indicate that the investigated compound was mixed type inhibitor. Molecular modelling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters. Quantum chemical parameters were studied by DFT BLYP 6-31G (d,p) basis set. The energy of the HOMO (EHOMO) provides information about the tendency of the molecule to donate electrons to an electron poor species. The higher the (EHOMO) is the greater tendency of a molecule to donate its electrons to the electron poor species. Therefore the studied compound provides an indication that it would have highest tendency to donate its electrons to the metal surface and therefore bind strongly to the metal surface. Adsorption sites is mainly over the Nitrogen atoms.
CORRELATION BETWEEN INHIBITION EFFICIENCY AND CHEMICAL STRUCTURE OF NEW INDOLO IMIDAZOLINE ON THE CORROSION OF MILD STEEL IN MOLAR HCL WITH DFT EVIDENCES
(Oriental Journal of Chemistry, 2015-06-12) Sowmya, Ramkumar; D, Nalini
The present work aims at the synthesis, characterization and study on the inhibitive effect of indoloimidazoline derivative (DI) on mild steel in 1M HCl. Weight loss measurement and electrochemical AC and DC corrosion monitoring techniques are performed at 308 K using mild steel specimens immersed in 1M HCl in the presence and absence of DI. Polarisation curves indicated that DI acted as a mixed type inhibitor. The indoloimidazoline derivative having nitrogen atoms in its molecular structure are adsorbed on the metal surface through these active centres and that the extent of inhibition is directly related to the formation of the adsorption layer according to Langmuir isotherm model on the mild steel surface which is sensitive function of the molecular structure. Quantum chemical calculations performed using DFT B3LYP 6-31G (d, p) basis set within the program Gaussian 09 showed the adsorption sites for DI on mild steel. Experimental and theoretical findings agreed well with each other
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 ABATEMENT IN ACID PICKLING INDUSTRIES BY EFFECTIVE N-HETEROCYCLIC COMPOUNDS: DRY AND WET LAB STUDIES
(NACE International, 2016) SowmyaRamkumar; D, Nalini
During the chemical cleaning process using acids, in many electroplating and other descaling industries, there exists the problem of heavy metal loss. Hence there is always a need for abatement of this metal loss. A critical (steady state) value of the resistivity to corrosion of two organic compounds, 5-[2-(4-methoxyphenyl)-vinyl]-3-phenyl isoxazole (MVI) and 5-[2-(4-methoxyphenyl)-vinyl]-1,3,8-triaza-cyclopenta[a]indene (MCI) were determined by a combination of non-electrochemical and electrochemical monitoring techniques. The behavior of organic compound, on a metallic alloy, i.e., mild steel, was investigated over a temperature range of 30 to 70°C. Efficiency of MVI and MCI were determined by correlating the electrochemical response of the compound (by electrochemical impedance and potentiodynamic polarization) in 1M HCl and 0.5M H2SO4 solution with their structural features. EIS measurement predicted the physical adsorption of both MVI and MCI on the metal surface from PZC calculation. Polarization studies proved that the inhibitors retard both the electrode process during inhibition. The integrity of the inhibitors efficiency with respect to time was assessed from mass loss measurements at different immersion period. Mass loss measurements proved that both MVI and MCI inhibit corrosion of mild steel in 1M HCl with a maximum efficiency of 91.07% and 78.23% at 20 ppm in HCl and H2SO4 respectively for MVI, 97.72% and 88.64% at 20 ppm in HCl and H2SO4 respectively for MCI. Hence MVI and MCI were found to be effective inhibitors for acid cleaning process in industries. The mechanism of the inhibition process was discussed in the light of the chemical structure and quantum chemical calculations of the investigated inhibitor. MVI and MCI were modeled in order to assess its absorbability using density functional theory (DFT) and revealed remarkably high interaction energies, which corroborate the experimental findings.
RELIABLE CORROSION INHIBITION OF MILD STEEL DURING ACID DESCALING USINGORGANIC NITROGENOUS COMPOUND: A COMBINED ELECTROCHEMICAL ANDCOMPUTATIONAL ASSESSMENT
(NIGIS, 2016) SowmyaRamkumar; D, Nalini
The objective of this paper is to give an overview assessment for alleviation of metal lossconsidering internal corrosion protection, safety aspects and meets industrial requirements. Theultimate goal of this study is to have inhibitor for mild steel protected against corrosive environmentsin order to mitigate heavy metal loss during acid pickling. Acid- used to reduce the formationdamage around the oil well or to remove scale - readily attacks the metal. In the oil extraction andprocessing industries, inhibitors have been considered to be the first line of defense againstcorrosion. Most of the inhibitors currently used in producing wells are organic nitrogenouscompounds. The present work aims at the study of a new imidazoline derivative, 2-[2-(4-Nitrophenyl)-vinyl]-tetrahydro-1,3,8-triaza-cyclopenta[a]indene (NVI) as mild steel corrosion inhibitor inH2SO4 acid medium by electrochemical methods. NVI was found to inhibit corrosion with efficiencyabove 85 % in sulphuric acid medium. Electrochemical impedance studies proved that NVI inhibitsmetal loss by physically adsorbing on the surface through its hetero atoms. Polarization studiesproved the mixed mode of inhibition by NVI. Theoretical evidences obtained by structuraloptimization of NVI using GAUSSIAN software employing DFT also support the experimentalfinding.
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.
SUBSTITUTED 2-IMIDAZOLINE DERIVATIVE: NEW AND EFFICIENT CORROSION INHIBITORS FOR MILD STEEL IN SULPHURIC ACID SOLUTION
(SASEST, 2014-08-21) SowmyaRamkumar; D, Nalini; R, Rajalakshmi
The aim of this work is to obtain deeper insight into the mechanism of the protective action of the imidazole-based corrosion inhibitor, 2-(4’-N, N-Dimethylaminophenyl)-imidazoline (DMAP2I). Investigations were performed on mild steel in 0.5 M H2SO4 by electrochemical methods and non - electrochemical methods. Maximum protection efficiency reaches about 85% for DMAP2I at 200 ppm concentration level. The adsorption of the imidazoline derivative on mild steel surface follows Langmuir and Tempkin isotherm. The adsorption free energy on mild steel (20 – 30 kJ/mol) reveals a comprehensive (physical and chemical) adsorption of the inhibitors on the metal surface. Polarization curves reveal that DMAP2I act as a mixed-type inhibitor. Results obtained from potentiodynamic polarization and impedance measurements are in good agreement. Quantum chemical method is used to explore the relationship between the inhibitor molecular properties and its inhibition efficiency. The density function theory (DFT) is also used to study the structural properties of the inhibitor. It is found that when the imidazole derivative adsorbs on the mild steel surface, molecular structure influences their interaction mechanism. The inhibition efficiencies of the compound showed a certain relationship to highest occupied molecular orbital (HOMO) energy and Mulliken atomic charges.