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Author: search.filters.author.Nalini, DEnd date: 2019

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    INHIBITION OF MILD STEEL CORROSION IN THE PRESENCE OF P-NITROPHENYL-2- IMIDAZOLINE
    (NACE - International Corrosion Conference Series, 2013-03-17) Nalini, D; Rajalakshmi, R
    p-nitrophenyl-2-imidazoline (PNP2I) was synthesized in the laboratory and characterized by Fourier Transform Infrared Spectroscopy (FTIR) spectra and evaluated as a corrosion inhibitor for mild steel in 1M Hydrochloric acid and 0.5M Sulphuric acid by weight loss method and electrochemical studies. Results obtained revealed that PNP2I was a very good inhibitor and behaved better in 0.5M H2SO4 than in 1M HCl. Potentiodynamic polarization curves showed that PNP2I is a mixed type inhibitor. The ability of the studied inhibitor to inhibit the corrosion of mild steel was due to the presence of two hetero nitrogen atoms on the imidazoline ring and the phenyl ring attached to the imidazoline ring. The adsorption of PNP2I on the mild steel surface in both acidic media followed the Langmuir adsorption isotherm. Surface analyses were also carried out, to establish the mechanism of the corrosion inhibition of mild steel in acidic solutions. Good inhibition efficiency was evidenced in both acid solutions, furnishing an inhibition efficiency of 80 %.
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    SELECTIVE BIS-N-ARYL THIOSEMICARBAZONES AS EFFICIENT CORROSION INHIBITORS
    (ProQuest, 2010-07-29) Shamitha Begum, A; Nalini, D; Suvarnna, K
    The study of the effect of the Bis-N-aryl thiosemicarbazone compounds on the corrosion behaviour of mild steel in 1M sulphuric acid and in1M hydrochloric acid shows that these compounds are very efficient inhibitors. Their inhibition efficiency increased with increase in concentration and also increased with temperature. The inhibitors showed a mixed type of inhibition in potentiodynamic polarization study and in impedance method in presence and absence of inhibitors. The adsorption of inhibition followed Langmuir adsorption isotherm. The thermodynamic parameters such as activation energy (Ea) and free energy of adsorption Gads were calculated. The Ea value of the uninhibited solution was less than the inhibited solutions revealing chemisorption of the inhibitor on the mild surface.
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    SYNTHESIS, CHARACTERIZATION AND CORROSION PROTECTIVE EFFICIENCY OF SOME 1,3,4-THIADIAZOLINES ON MILD STEEL IN ACID MEDIA
    (Oriental Journal of Chemistry, 2010) Shamitha Begum, A; Nalini, D; Manjula Devi, T
    The Inhibition effect of corrosion of mild steel using Thiadiazolines in H2SO4 medium by weight loss, electrochemical methods was investigated. The corrosion inhibition was studied in H2SO 4 by weight loss method for about 3hrs at room temperature and It was found that the corrosion inhibition behaviour of Thiadiazolines is greater in sulphuric acid. Results were fitted into suitable adsorption isotherm. The Electrochemical parameters for mild steel in H2SO4 solution with and without inhibitor were calculated. The data revealed that Electrochemical polarization shows the Mixed Mode of inhibition and the results of Electrochemical impedance spectroscopy have shown that the change in the impedance parameters, charge transfer resistance and double layer capacitance with the change in concentration of the inhibitor is due to the adsorption of the molecules leading to the formation of a protective layer on the surface of mild steel. The Effect of Temperature on the corrosion rate, activation energy and free energy of adsorption were also calculated.
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    ENHANCED CORROSION RESISTANCE OF MILD STEEL IN SULPHURIC ACID MEDIUM BY IMIDAZOLE DERIVATIVE: EXPERIMENTAL AND COMPUTATIONAL STUDIES
    (Elsevier, 2019) Sowmya, Ramkumar; Nalini, D
    The inhibition action of the imidazole derivative on the corrosion of mild steel in 0.5 M Sulphuric acid was investigated by weight loss, polarization, Impedance and SEM. The PZC of mild steel was studied by AC impedance method. The polarization experiment revealed that IDZ is of mixed–type but slightly anodic control. Weight loss results obtained revealed that the imidazoline derivatives performed excellently as corrosion inhibitor with efficiency above 70% at 20ppm at 303 K. The optimum period of inhibition for IDZ was determined by weight loss studies. Its adsorption on mild steel obeys Tempkin isotherm. Quantum chemical parameters and Mulliken charge densities on the optimized structure of imidazoline derivative were calculated using GAUSSIAN 09 with B3LYP / 6-31G (d,p) basis set
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    MACROCYCLIC COMPOUNDS AS GREEN CORROSION INHIBITORS FOR ALUMINIUM: ELECTROCHEMICAL, SURFACE AND QUANTUM CHEMICAL STUDIES
    (International Journal of Corrosion and Scale Inhibition, 2018-09-28) Ansari, K R; Ramkumar, S; Chauhan, D S; Salman, Md; Nalini, D; Srivastava, V; Quraishi, M A
    In the present work, two macrocyclic compounds namely 5,6,11,12-tetramethyl1,2,4,7,8,10 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 1H NMR and 13C 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 quantum chemical parameters corroborated the experimental observations and suggested a better performance of TMCD compared to TMPD molecule.
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    INFLUENCE OF SOIL FUNGI ON CORROSION OF MILD STEEL PLATES
    (NACE - International Corrosion Conference Series, 2018-04-15) Dharani, R; Deepalakshmi, R; Padma Devi, S N; Nithya Meenakshi, S; Nalini, D
    Metal corrosion is an electrochemical reaction between the environment and a metal, in which microbes are thought to play a very important role. These microorganisms do not only cause corrosion, but they can also inhibit or protect against corrosion. Fungi are the most dessicant – resistant microorganisms and are ubiquitous in atmospheric environments. About five fungal organisms were isolated using Starkey media from the soil of corroded pipeline tank. The influence of these fungal isolates on both rusted and non – rusted mild steel plates were studied for a period of 25 days. Among the five fungal isolates, Non – rusted Isolate (NR) – 1 and Rusted Isolate (R) – 3 showed minimum corrosion reaction on mild steel plates, based on the results of weight loss and dissolved iron content. The results revealed that the two isolates showed minimum rate of corrosion on mild steel plates due to the passive mechanism of microbes upon the plates. Therefore the above isolates (NR -1 and R- 3) was identified using molecular markers and it was found to be Aspergillus flavus and Alternaria alternata respectively.
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    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; Nalini, D
    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.
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    CORROSION INHIBITION OF MILD STEEL IN ACIDIC MEDIA BY 5′-PHENYL-2′,4′-DIHYDROSPIRO[INDOLE-3,3′-PYRAZOL]-2(1H)-ONE
    (Hindawi Publishing Corporation, 2013) Jannathul Firdhouse, M; Nalini, D
    The inhibition effect of -phenyl-,-dihydrospiro[indole-3,-pyrazol]-2(1H)-one (SPAH) on mild steel corrosion in 1 M HCl and 0.5 M H2SO4 has been studied by weight loss, effect of temperature, electrochemical techniques, and quantum chemical studies. The inhibition efficiency increases with increasing concentration of inhibitor but decreases with increase in temperature. The adsorption of inhibitor on mild steel surface has been found to obey Langmuir and Temkin’s adsorption isotherm. Potentiostatic polarization results revealed that SPAH acts as mixed type inhibitor. The values of activation energy (), free energy of adsorption (), enthalpy of adsorption (), and entropy of adsorption () were calculated. Surface analysis (SEM) was also carried out to establish the mechanism of inhibitor on mild steel corrosion in acid medium. Quantum chemical studies using DFT were employed to explain the experimental results obtained in this study and to further give insight into the inhibition action of SPAH on the mild steel surface.
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    CORROSION ABATEMENT IN ACID PICKLING INDUSTRIES BY EFFECTIVE N-HETEROCYCLIC COMPOUNDS: DRY AND WET LAB STUDIES
    (NACE - International Corrosion Conference Series, 2016-03-06) Sowmya, Ramkumar; Nalini, D
    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-triazacyclopenta[ 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.
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    A COMBINED EXPERIMENTAL AND THEORETICAL INVESTIGATION ON PYRAZOLONE DERIVATIVE AS CORROSION INHIBITOR FOR MILD STEEL IN 0.5 M SULPHURIC ACID MEDIA
    (Portugaliae Electrochimica Acta, 2014-04-23) Nalini, D; Kohilah, K S; Sowmya, Ramkumar
    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 ∆G° 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.