Electrochemical and quantum chemical parameters of

Heliyon, 2020

The corrosion inhibition displays of two quinoxaline derivatives, on the corrosion of M-steel (M-steel) in 1 M HCl was studied by gravimetric, electrochemical, scanning electron microscopy (SEM), functional density theory (DFT) and molecular dynamic simulation (MD). The inhibitory efficacy increases with decreasing temperature and increases with inhibitor concentration and reached to 96 % (NSQN) and 92 % (CSQN) at 303 K and the optimum concentration (1Â10-3 M). Ultraviolet-visible (UV-vis) spectroscopic analyses confirmed the presence of chemical interactions between the inhibitors and MS surface. The adsorption of NSQN & CSQN on the metallic surface obeys the Langmuir isotherm. A potentiodynamic polarization study confirmed that the inhibitors are of mixed-kind inhibitors. Theoretical computation (DFT) and molecular dynamics simulation (MD) are utilized to understand the mechanism of inhibition.

Journal of Dispersion Science and Technology, 2012

The use of nitrogen and sulphur donor organic inhibitors in acid solutions is a common method for the protection of metals from corrosion. The present work is the study of the corrosion inhibition efficiency of (E)-4-(2-chlorobenzylideneamino)-6methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (CBMTDT) towards mild steel in 1 M HCl. The work strategy includes the conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), electrochemical impedance spectroscopy (EIS), adsorption studies and quantum chemical calculations. Results showed that the corrosion rate decreases and inhibition efficiency increases with inhibitor concentration. The results of polarization studies reveal that the additive acts as a mixed type inhibitor. The surface adsorption of the inhibitor molecules decreases the double layer capacitance and increases the polarization resistance. The adsorption process is spontaneous and follows Langmuir adsorption isotherm model. The optimized structure of the inhibitor, energies of LUMO, HOMO and other physical parameters are calculated by computational quantum chemical methods.

Journal of Adhesion Science and Technology, 2019

The blocking of corrosive sites of soft (mild) steel has been studied using ravage drugs Pyrazinamide (Z), Isoniazid (H) and Rifampicin (R) in 0.5 M HCl medium. The degree of ability of these drugs to act as corrosion controlling agents was investigated by gravimetric measurements, potentiostatic polarization and electrochemical impedance spectroscopy. Their inhibition efficacy has, further been validated through theoretical and simulation studies. Though, all the drugs have shown good anticorrosive impact, but, rifampicin (R) has proven its greater efficacy as 97.06% at 1000 ppm and at 303 K. Polarization curves depict that the H and R drugs act through mixed mode of inhibition while Z drug is predominantly anodic in nature. The result of electrochemical impedance spectroscopy specifies that the corrosion reaction is resisted by charge transfer process. Morphology of un-corroded and corroded coupons was studied by scanning electron microscopy. The mechanism of adsorption is obeyed well through Langmuir isotherm and advocated a significant physiochemical type of interaction by the compounds on the metal surface. Thus, all the findings got via various experimental techniques along with that of obtained using Molecular Dynamics (MD) and Density Functional Theory (DFT) for the three compounds are in proper harmony.

Chinese Journal of Chemical Engineering, 2020

This work is devoted to the study of the inhibition of corrosion of mild steel (MS) in molar hydrochloric acid (1 mol⋅L-1 HCl) by two named quinoxaline derivatives namely, 2-(2,4-dichlorophenyl)-1,4-dihydroquinoxaline (HQ) and 2-(2,4-dichlorophenyl)-6-methyl-1,4-dihydroquinoxaline (CQ). The inhibitory efficacy of HQ and CQ compounds is first evaluated using the gravimetric method and using electrochemical techniques (stationary and transient techniques). The results showed that our compounds are efficient corrosion inhibitors and the inhibition rates (η EIS %) reached up to 91% and 94.2% at 10 −3 mol⋅L-1 for HQ and CQ, respectively. The mentioned molecules are classified as mixed-type inhibitors. The adsorption of these inhibitors on the surface of steel in hydrochloric HCl 1 mol⋅L-1 medium obeys the Langmuir adsorption isotherm. The results of the scanning electron microscope (SEM) showed the formation of a protective film on the surface of the steel in the presence of the inhibitors studied. Elementary analysis is obtained by energy dispersive X-ray spectroscopy (EDS). The inhibition property was further elucidated by theoretical approaches such as: Density Functional Theory (DFT), quantum chemical descriptors (QCD), local reactive indices, solvent effect, theoretical complexation, Molecular Dynamic (MD) simulation, effect of temperature on adsorption energy (E ads), Radial Distribution Function (RDF), and Mean Square Displacement (MSD). The results of these approaches support the experimental results.

Bulletin of Materials Science, 2008

In the present investigation a new corrosion inhibitor, N′-(3,4-dihydroxybenzylidene)-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(DHBTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H 2 SO 4 (0⋅5 M, 1 M) solutions using weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency measured by all the above three techniques were in good agreement with each other. The results showed that DHBTPH is a very good inhibitor for mild steel in acidic media. The inhibition efficiency in different acid media was found to be in the decreasing order 0⋅5 M H 2 SO 4 > 1 M HCl > 1 M H 2 SO 4 > 2 M HCl. The inhibition efficiency increases with increasing inhibitor concentration and with increasing temperature. It acts as an anodic inhibitor. Thermodynamic and activation parameters are discussed. Adsorption of DHBTPH was found to follow the Langmuir's adsorption isotherm. Chemisorption mechanism is proposed. The mild steel samples were also analysed by scanning electron microscopy (SEM).

The inhibition of mild steel corrosion in 1 M HCl by four 5-arylpyrimido- [4,5-b]quinoline-diones (APQDs), namely 5-(4-nitrophenyl)-5,10-dihydropyrimido [4,5-b]quinoline-2,4(1H,3H)-dione (APQD-1), 5-phenyl-5,10dihydropyrimido[4,5-b]quinoline-2,4(1H,3H)-dione (APQD-2), 5-(4-hydroxyphenyl)-5,10-dihydropyrimido-[4,5-b]quinoline-2,4(1H,3H)-dione (APQD-3) and 5-(2,4-dihydroxyphenyl)-5,10-dihydropyrimido [4,5-b] quinoline-2,4(1H,3H)-dione (APQD-4) has been investigated using weight loss, electrochemical, surface, and quantum chemical calculations and molecular dynamics simulation methods. The results showed that the inhibition efficiency (h%) increased with increasing concentration of the inhibitors. Among the studied compounds, APQD-4 exhibited the highest inhibition efficiency of 98.30% at 20 mg l À1 concentration. The studied compounds effectively retarded the corrosion of mild steel in 1 M HCl by adsorbing onto the steel surface, and the adsorption data conformed to the Langmuir adsorption isotherm. The results of potentiodynamic polarization measurements revealed that the studied compounds are cathodic-type inhibitors. Scanning electron microscopy (SEM) study confirmed the formation of adsorbed films of the inhibitor molecules on the steel surface. Quantum chemical calculations and molecular dynamics simulations were undertaken to corroborate experimental findings and provide adequate insight into the corrosion inhibition mechanisms and adsorption characteristics of the studied compounds.

Derivatives of piperazine (Tert-butyl-4-(2-(ethoxycarbonyl)benzofuran-5-yl)-piperazine-1-carboxylate, Ethyl 5-(piperazin-1-yl)benzofuran-2-carboxylate and 3tert-butyl 4-(2-carbamoylbenzofuran-5-yl)piperazine-1-carboxylate) were used as corrosion inhibitors for mild steel in hydrochloric acid solution. The inhibition efficiency depended on the concentration and type of the piperazines. The inhibition efficiency ranged between 90 and 94 % at the highest concentration (25 mM), and between 44 and 62% at the lowest concentration (5 mM) of inhibitor in 1 M HCl solution. Inhibition efficiency decreased with rise in temperature, this corresponded to surface coverage of the metal by the inhibitor. Potentiodynamic polarization measurements have been carried out at room temperature, which clearly reveal the fact that all investigated inhibitors are of mixed type and they inhibit corrosion of mild steel by blocking the active sites of the metal surface. The results also showed that, the inhibitors were adsorbed on the mild steel surface according to Langmuir adsorption isotherm.

Portugaliae Electrochimica Acta, 2018

The corrosion inhibition of carbon steel in a 1.0 M HCl solution, using 4-amino-2-(4 chlorophenyl)-8-(2,3-dimethoxyphenyl)-6-oxo-2,6-dihydropyrimido[2,1b][1,3]thiazine-3,7-dicarbonitrile (ACMPT) was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemical calculations. Polarization curves indicate that the studied compound was acting as a mixed inhibitor with predominant cathodic effectiveness. The inhibition efficiency decreased with an increased temperature, and the thermodynamic and activation parameters obtained from this study were discussed. The adsorption behavior of ACMT follows Langmuir's isotherm. In addition, Density Function Theory (DFT) calculations were performed on the studied molecule. The theoretical parameters obtained from this method are in good agreement with the experimental results.

2017

The new derivative of 1, 2,3-triazole in basic 8-hydroxyquinoline namely ethyl 4-amino-1-((8-hydroxyquinolin-5-yl)methyl)-1H-1,2,3-triazole-5-carboxylate (EHTC) was synthesized and characterized by NMR spectroscopic. This compound was tested as corrosion inhibitor for carbon steel in a 1.0 M HCl solution using Gravimetric, potentiodynamic polarization curves and electrochemical impedance spectroscopy. Potentiodynamic polarization curves measurements showed that the investigated compound acts as mixte-type inhibitor. Its inhibition efficiency improved with concentration and reached a maximum 91 % at 10-3 M. In addition, the temperature effect on the in the inhibition efficiency of EHTC was also studied in the temperature range of 298-328 K. It is found that the inhibition efficiency decreases with temperature. Indeed, the adsorption of the studied inhibitor on the mild steel was well described by the Langmuir isotherm and the calculated ΔG * ads value showed that corrosion inhibition was controlled by a chemisorptions process. Quantum chemical calculations were used to correlate the inhibition ability of EHTC with its electronic structural parameters.

Journal of Electrochemical Science and Engineering

Interaction of metal surfaces with organic molecules has a significant role in corrosion inhibition of metals and alloys. More clarification, from both experimental and computa­tional view is needed in describing the application of inhibitors for protection of metal surfaces. In this study, the surface adsorption and corrosion inhibition behavior of metol­azone, a quinazoline derivative, on mild steel in 0.02, 0.04, 0.06, and 0.08 M HCl solutions were investigated. Weight loss, potentiodynamic polarization and electrochemical impe­dance spectroscopy techniques were used. The optimum inhibition efficiencies of 75, 82 and 83 % were found by these three techniques at the optimum inhibitor concentration of 500 mg/L and 303 K. Scanning electron microscopy (SEM) was used to confirm adsorption of quinazoline derivative on the surface of the mild steel. Computational simulations were additionally used to give insights into the interaction between quinazoline inhibitor and mild steel surface...