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Author: search.filters.author.Nalini, D

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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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    AN AMINO ACID GRAFTED GRAPHENE OXIDE AS PROMISING MATERIAL IN POLY(UREA-FORMALDEHYDE)-EPOXY MICROCAPSULES FOR ENHANCING THE INTERFACIAL ADHESION OF EPOXY COATINGS (Article)
    (Asian Publication Corporation, 2023-03) Priyanka, D; Nalini, D
    Novel microencapsulated materials with superior anti-corrosion properties and improved adhesive strength on the metal substrate were produced by emulsion polymerization and characterized successfully. Initially, serine grafted graphene oxide was prepared and characterized through various sophisticated techniques. Then, MC-GO/epoxy and MC-GO-Ser were individually impregnated into th epoxy system and applied on the mild steel substrates. Corrosion tests were performed to evaluate the non-corrosive nature of MC-GO/epoxy and MC-GO-Ser/epoxy samples. After 7 days of exposure in saline media, MC-GO-Ser microcapsules demonstrated 80.6 % protective efficiency. Furthermore, the peel strength of 2.90 N revealed that the coating loaded with MC-GO-Ser microcapsules had improved adherence to the mild steel surface. Results of urea-formaldehyde GO-Ser microcapsules showed better corrosion protection and greater adhesive strength, which is probably because of the exceptional barrier action of microcapsules against the incursion of corrosion solution onto the mild steel surface.
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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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    TRIAZOLES AS POTENTIAL CORROSION INHIBITORS: RECENT DEVELOPMENTS AND FUTURE PERSPECTIVES
    (Elsevier, 2023) Ramkumar, S; Nalini, D; Chauhan, D S; Quraishi, M A
    Industries are continuously searching for solutions to reduce the losses caused by the massive issue of corrosion, which consumes company earnings. Prevention is the best defense against corrosion. Customized solutions using various corrosion inhibitors are one of the best methods of corrosion prevention. Organic compounds rich in heteroatoms and electron-rich cores, serve as barriers that prevent corrosion by forming an adsorbed layer. Triazoles stand out as a significant five-member nitrogen heterocycle among nitrogen-containing heterocyclic compounds with outstanding uses. Five-membered triazole come in two different structural varieties: 1,2,3-triazole and 1,2,4-triazole. Both 1,2,3- and 1,2,4-triazoles may support a wide range of substituents (electrophiles and nucleophiles) around the core structures due to their structural features, which allows for the development of numerous unique compounds. The excellent corrosion protection action of triazole derivatives can be attributed to the presence of electron-withdrawing and electron-donating substituents that allow an improved protection performance compared to that of the parent triazole molecule. Computational studies have provided evidence that the triazole- based molecules undergo donor-acceptor type interactions with metallic substrates. Triazoles are used in a variety of commercial applications, including physiologically active compounds, agrochemicals, corrosion inhibitors, dyes, and optical brighteners. This paper deals with the review on recent developments on triazole as corrosion inhibitors and their application as corrosion inhibitors and their recent trends in the field of corrosion of different metals in a variety of corrosive environments.
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    ANTI-CORROSIVE PROPERTY OF BIOINSPIRED ENVIRONMENTAL BENIGN IMIDAZOLE AND ISOXAZOLINE HETEROCYCLICS: A CUMULATIVE STUDIES OF EXPERIMENTAL AND DFT METHODS
    (Wiley, 2020) Sowmya, Ramkumar; Nalini, D; 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.
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    INHIBITORY ACTION OF MACARANGA PELTATA LEAVES EXTRACT ON THE CORROSION OF MILD STEEL IN 0.5 M SULPHURIC ACID- QUANTUM CHEMICAL APPROACH
    (Elsevier, 2020) Athul, K K; Thilagavathy, P; Nalini, D
    Weight loss and electrochemical impedance spectroscopy (EIS) method were used for testing the corrosion inhibition effect of Macaranga peltata leaves (MPL) extract on corrosion of mild steel in 0.5 M sulphuric acid solution. The inhibitory effect of MPL was studied at various concentrations of the extract and different time of immersion. In all cases an optimal efficiency was found out. Maximum inhibition efficiency was 92.6% for 5%v/v at 5 h. Nyquist and Tafel plots gave a confirmation about the inhibitory action of the plant extract, agreeing with the weight loss method. The surface content of mild steel after immersion was investigated using IR and the inhibition mechanism is suggested as adsorption of the phytochemical constituents from the results. The Quantum chemical energy calculations become an additional support of the suggested mechanism.
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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.