Browsing by Author "Chauhan D S"

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CHEMINFORMATIC SCRUTINY OF SOME HETEROCYCLIC COMPOUNDS FOR THEIR CORROSION PROTECTIVE CAPABILITY
(International Journal of Corrosion and Scale Inhibition, 2021-12-27) Ramkumar S; Nalini D; Priyanka D; Qurashi M A; Chauhan D S
Over the last two decades, molecular modellings are capable of accurately predicting structures, energetics, reactivity, and other properties of molecules. Computational chemistry plays an important role in enabling chemists to: (i) explain and rationalize known chemistry of corrosion inhibitors and (ii) explore new or unknown chemicals applicable as corrosion inhibitors. In contrast to the traditional techniques of identifying and synthesizing new corrosion inhibitors in the wet lab, a prior dry-lab process is suggested by using cheminformatics tools. Once a correlation between the structure and activity or property is found, any number of compounds can be readily screened employing computational methodology. In the present work, the inhibitive performance of three important classes of heterocyclic compounds namely dithiazolidine, thioamidine, and thiourea derivatives have been calculated using quantum chemical methods. The three selected heterocyclic series contains nitrogen and sulphur in their chemical framework that were expected to be the main electron rich centres which act as the adsorption sites on the metal surface. The presence of aromatic ring together with electron donating substituents such as methyl and methoxy were found to enhance the adsorption characteristics of the studied heterocyclic systems. The global reactivity parameters and the local selectivity adsorption centres in each of the studied system were analyzed using theoretical parameters.
CHEMINFORMATIC SCRUTINY OF SOME HETEROCYCLIC COMPOUNDS FOR THEIR CORROSION PROTECTIVE CAPABILITY
(International Journal of Corrosion and Scale Inhibition, 2021-12-27) Ramkumar S; Nalini D; Priyanka D; Qurashi M A; Chauhan D S
Over the last two decades, molecular modellings are capable of accurately predicting structures, energetics, reactivity, and other properties of molecules. Computational chemistry plays an important role in enabling chemists to: (i) explain and rationalize known chemistry of corrosion inhibitors and (ii) explore new or unknown chemicals applicable as corrosion inhibitors. In contrast to the traditional techniques of identifying and synthesizing new corrosion inhibitors in the wet lab, a prior dry-lab process is suggested by using cheminformatics tools. Once a correlation between the structure and activity or property is found, any number of compounds can be readily screened employing computational methodology. In the present work, the inhibitive performance of three important classes of heterocyclic compounds namely dithiazolidine, thioamidine, and thiourea derivatives have been calculated using quantum chemical methods. The three selected heterocyclic series contains nitrogen and sulphur in their chemical framework that were expected to be the main electron rich centres which act as the adsorption sites on the metal surface. The presence of aromatic ring together with electron donating substituents such as methyl and methoxy were found to enhance the adsorption characteristics of the studied heterocyclic systems. The global reactivity parameters and the local selectivity adsorption centres in each of the studied system were analyzed using theoretical parameters
GRAPHENE OXIDE INTEGRATED INTO PROTECTIVE COATINGS AGAINST CORROSION FOR METALS AND ITS ALLOYS: A REVIEW
(International Journal of Corrosion and Scale Inhibition, 2022-04-02) Priyanka D; Vinuchakravarthi S; Nalini D; Quraishi M A; Chauhan D S
This review aims to discuss the effect of graphene oxide (GO) derivatives incorporated protective coatings on various metals against corrosion process in alkaline environments. These coatings increased hydrophobic character and adhesion strength between the coating and metal surface. Electrochemical measurements were used more often among all other techniques to investigate the effect of inhibitor in the polymer matrix (epoxy/silane sol). In some cases, the highest inhibition efficiency was achieved by electrochemically coating GO derivatives on the metal surface. GO derivatives prepared via the adsorption of Pr3+, Ce3+,and Zn2+ ions have revealed a good inhibition tendency for metals in acidic solution because of the exchange of Pr3+, Ce3+, and Zn2+ with those ions (Na+ , Cl–) in the corrosion electrolyte. Further, because of the adsorption of polar groups on GO onto the surface of metals, the hydrophobicity achieved by modified GO coating limits the infiltration of corrosive ions and enhances inhibitory efficiency. And, scratches were foreseen during the manufacturing of coatings on metallic substrates, and this harms the organic coatings. The defect created by impurities developed coatings deterioration that was prone to the diffusion of corrosive substances, severely reducing the coatings’ lifespan. Grafting graphene oxide with various functional groups was used to achieve self-healing behavior in organic coatings. At the defective site of the metallic substrates, self-healing by functionalized graphene oxide created dense protective coatings.
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.