Chandrabhan Verma

L-Proline-promoted synthesis of 2-amino-4-arylquinoline-3-carbonitriles as sustainable corrosion inhibitors for mild steel in 1 M HCl: experimental and computational studies

The inhibition of mild steel corrosion in 1 M HCl by 2-amino-4-(4-nitrophenyl) quinoline-3-carbonitrile (AAC-1), 2-amino-4-phenylquinoline-3-carbonitrile (AAC-2) and 2-amino-4-(4-hydroxyphenyl) quinoline-3-carbonitrile (AAC-3) has been investigated using weight loss, electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)), surface (SEM, EDX and AFM) and quantum chemical calculation methods. The results indicated that the investigated inhibitors exhibited good inhibition efficiency against the corrosion of mild steel in acidic solution. The weight loss and electrochemical results suggested that inhibition efficiencies were enhanced with an increase in the concentration of 2-amino-4-arylquinoline-3-carbonitriles (AACs). The results showed that the inhibition efficiencies of the investigated AACs obeyed the order: AAC-3 (96.52%), AAC-2 (95.65%) and AAC-1 (94.78%). Potentiodynamic polarization study revealed that the investigated AACs act as cathodic type inhibitors. Adsorption of the AACs on a mild steel surface obeyed the Langmuir adsorption isotherm. Furthermore, SEM, EDX and AFM studies clearly revealed the film-forming ability of AACs on the mild steel surface. Quantum chemical calculations were undertaken to provide mechanistic insight into the mechanism of inhibition action of AACs. On the basis of experimental and theoretical studies it was concluded that the presence of electron releasing hydroxyl (–OH) groups in AAC-3 increases the inhibition efficiency whereas electron withdrawing nitro (–NO2) groups in AAC-1 decrease the inhibition efficiency.

5-Arylpyrimido-[4,5-b]quinoline-diones as new and sustainable corrosion inhibitors for mild steel in 1 M HCl: a combined experimental and theoretical approach

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-5,10-dihydropyrimido[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 (η%) 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−1 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.

2,4-Diamino-5-(phenylthio)-5H-chromeno [2,3-b] pyridine-3-carbonitriles as green and effective corrosion inhibitors: gravimetric, electrochemical, surface morphology and theoretical studies

The inhibition of mild steel corrosion in 1 M HCl by three newly synthesized 2,4-diamino-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitriles (DHPCs) namely, 2,4-diamino-7-nitro-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-1), 2,4-diamino-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-2) and 2,4-diamino-7-hydroxy-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-3) was studied using weight loss method, electrochemical techniques, surface morphology (SEM, AFM) studies and theoretical (quantum chemical calculations and molecular dynamic simulation) methods. The weight loss and electrochemical measurements showed that the inhibition efficiency increases with increasing inhibitor concentration and the relative trend of inhibition performance is DHPC-3 > DHPC-2 > DHPC-1. A potentiodynamic polarization study reveals that the investigated DHPCs act as mixed type inhibitors. The adsorption of the DHPCs on the mild steel surface obeys the Langmuir adsorption isotherm and involves both physisorption and chemisorption modes. The presence of the electron releasing –OH group at position seven on the chromenopyridine ring is considered to be responsible for the highest inhibition efficiency of DHPC-3 among the studied compounds. Whereas the presence of the electron withdrawing nitro (–NO2) group at position seven on the chromenopyridine ring is responsible for the lowest inhibitive strength of DHPC-1. Quantum chemical calculations and molecular dynamic simulation studies were undertaken to provide mechanistic insight into the roles of the different substituents (–OH and –NO2) on the corrosion inhibition behavior of the studied inhibitors.

A thermodynamical, electrochemical and surface investigation of Bis (indolyl) methanes as Green corrosion inhibitors for mild steel in 1 M hydrochloric acid solution

Abstract The influence of three Bis (indolyl) methanes (BIMs) namely, 3,3′-((4-nitrophenyl) methylene) bis (1H-indole) (BIM-1), 3,3′-(phenyl methylene) bis (1H-indole) (BIM-2) and 4-((1H-indol-2-yl)(1H-indol-3-yl) methyl) phenol (BIM-3) on the mild steel corrosion in 1 M HCl was studied by weight loss, electrochemical, scanning electron microscopy (SEM), and dispersive X-ray spectroscopy (EDX) methods. Results showed that BIM-3 shows maximum inhibition efficiency of 98.06% at 200 mg L−1 concentration. Polarization study revealed that the BIMs act as mixed type inhibitors. Adsorption of BIMs on the mild steel surface obeyed the Langmuir adsorption isotherm. The weight loss and electrochemical results were well supported by SEM and EDX studies.

5-Substituted 1H-tetrazoles as effective corrosion inhibitors for mild steel in 1 M hydrochloric acid

Abstract The corrosion inhibition efficiency of (E)-3-phenyl-2-(1H-tetrazole-5-yl)acrylonitrile (PTA), (E)-3-(4-nitrophenyl)-2-(1H-tetrazole-5-yl)acrylonitrile (NTA), and (E)-3-(4-hydroxyphenyl)-2-(1H-tetrazole-5-yl)acrylonitrile (HTA) on mild steel in 1 M HCl was tested using experimental and theoretical methods. The results show that the inhibition efficiency increases with the increasing concentration, and maximum values were obtained at a 40 mg L−1 concentration. The inhibition efficiency of the studied inhibitors follows the order HTA (98.69%) > NTA (96.60%) > PTA (93.99%). Polarization studies suggest that the tetrazoles behave as cathodic inhibitors. The adsorption of the tetrazoles on the mild steel surface obeys the Langmuir adsorption isotherm. In the present study, the values of the free energy of adsorption () vary from 34.92 to 39.71 kJ mol−1. The adsorption of the tetrazoles on the mild steel surface is supported by SEM, EDX and AFM studies. Quantum chemical calculations provide good support to the experimental results.

Corrosion inhibition of mild steel in 1M HCl by D-glucose derivatives of dihydropyrido [2,3-d:6,5-d′] dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone

D-glucose derivatives of dihydropyrido-[2,3-d:6,5-d′]-dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone (GPHs) have been synthesized and investigated as corrosion inhibitors for mild steel in 1M HCl solution using gravimetric, electrochemical, surface, quantum chemical calculations and Monte Carlo simulations methods. The order of inhibition efficiencies is GPH-3 > GPH-2 > GPH-1. The results further showed that the inhibitor molecules with electron releasing (-OH, -OCH3) substituents exhibit higher efficiency than the parent molecule without any substituents. Polarization study suggests that the studied compounds are mixed-type but exhibited predominantly cathodic inhibitive effect. The adsorption of these compounds on mild steel surface obeyed the Langmuir adsorption isotherm. SEM, EDX and AFM analyses were used to confirm the inhibitive actions of the molecules on mild steel surface. Quantum chemical (QC) calculations and Monte Carlo (MC) simulations studies were undertaken to further corroborate the experimental results.

Green Schiff's bases as corrosion inhibitors for mild steel in 1 M HCl solution: experimental and theoretical approach

Three cysteine based Schiffs bases namely 3-mercapto-2-((4-methoxybenzylidene)amino)propanoic acid (CSB-1), 2-((4-hydroxy-3-methoxybenzylidene)amino)-3-mercaptopropanoic acid (CSB-2) and 3-mercapto-2-(((E)-3-phenylallylidene)amino)propanoic acid (CSB-3) were synthesized and their corrosion inhibition properties on mild steel in 1 M HCl solution were evaluated using weight loss, electrochemical study and quantum chemical calculations. The result showed that CSB-3 is the best among the three studied inhibitors and showed the efficiency of 97.3% at 200 ppm concentration. The adsorption of inhibitors was found to be both physisorption and chemisorption and followed Langmuirs adsorption isotherm. SEM and AFM study also confirmed the formation of protective films of the inhibitors on mild steel surface. Potentiodynamic polarization studies revealed that all CSBs were of mixed type and predominantly behaved as cathodic inhibitors. EIS study showed that they inhibit corrosion by increasing the charge transfer resistance between metal–solution interfaces. Quantum chemical calculation parameters such as EHOMO, ELUMO, ΔE, global hardness and softness, electronegativity and fraction of electron transfer (ΔN) were calculated using DFT method to correlate the electronic properties with the adsorption behavior of studied Schiff bases.

New phosphonate based corrosion inhibitors for mild steel in hydrochloric acid useful for industrial pickling processes: experimental and theoretical approach

The present work deals with the synthesis and study of the inhibition effect of three α-aminophosphonates, namely diethyl (((4-chlorophenyl)amino)(phenyl)methyl)phosphonate (APCI-1), diethyl (((4-chlorophenyl)amino)(4-methoxyphenyl)methyl)phosphonate (APCI-2) and diethyl (1-((4-chlorophenyl)amino)-3-phenylallyl)phosphonate (APCI-3), on mild steel corrosion in 1 M hydrochloric acid solution using both experimental and theoretical methods. Weight loss results showed that the inhibition performance of the studied compounds increases with the concentration and the maximum inhibition efficiency was obtained at just 564 × 10−6 M concentration. Among all the three tested inhibitors, APCI-3 showed the best result having an inhibition efficiency of 96.90%. The potentiodynamic polarization study indicates that these α-aminophosphonates act as mixed type inhibitors and predominantly function as a cathodic inhibitor. Adsorption of the tested APCIs on the metallic surface obeyed the El-Awady adsorption isotherm. The adsorption of these compounds on the metallic surface was also supported by the scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. A good insight about the inhibition mechanism of the tested compounds was derived using DFT based quantum chemical calculations for their neutral as well as protonated forms. The orientation of inhibitors on the metallic surface and the interaction energies of these molecules were obtained using molecular dynamic simulation studies. Both experimental and theoretical studies suggested that the inhibition efficiency of the tested compounds followed the order APCI-3 > APCI-2 > APCI-1 and well corroborated each other.

Pyridine-based functionalized graphene oxides as a new class of corrosion inhibitors for mild steel: an experimental and DFT approach

The aims of the present work were to synthesise two functionalized graphene oxides, namely, diazo pyridine functionalized graphene oxide (DAZP-GO) and diamino pyridine functionalized graphene oxide (DAMP-GO), and to evaluate them as corrosion inhibitors on mild steel in 1 M hydrochloric acid. Electrochemical studies reveal that the inhibition efficiencies of both of the tested functionalized graphene oxides were enhanced with increasing concentration and the maximum inhibition efficiencies of 95.08% and 96.73% were obtained for DAMP-GO and DAZP-GO, respectively, at a concentration as low as 25 mg L−1. A potentiodynamic polarization study suggests that both DAZP-GO and DAMP-GO act as mixed type inhibitors with a slight cathodic predominance. The formation of a protective film on the mild steel surface was confirmed using scanning electron microscope, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy techniques. Dynamic functional theory parameters such as EHOMO, ELUMO, energy band gap (ΔE), electronegativity (χ), hardness (η), softness (σ) and a fraction of electron transfer (ΔN) were calculated to support the experimental results.

N-Methyl-N,N,N-trioctylammonium chloride as a novel and green corrosion inhibitor for mild steel in an acid chloride medium: electrochemical, DFT and MD studies

In the present work, N-methyl-N,N,N-trioctylammonium chloride (Aliquat 336) has been evaluated as a green and novel corrosion inhibitor for mild steel in a 1 M HCl solution using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and chemical, spectroscopic (FTIR and UV-visible) methods. The results show that Aliquat 336 is an effective corrosion inhibitor and showed the maximum inhibition efficiency of 94.6% at a very low concentration of 4.95 μM. The results of the EIS study showed that Aliquat 336 inhibits corrosion by an adsorption mechanism. The PDP results revealed that Aliquat 336 is a mixed type inhibitor, which predominantly acts as a cathodic inhibitor. The formation of an inhibitor film on the metal surface was corroborated by atomic force microscopy (AFM). The adsorption of Aliquat 336 on a mild steel surface obeys the Langmuir adsorption isotherm. Quantum chemical calculations (DFT based) and molecular dynamics (MD) simulation studies further corroborated the adsorption and inhibition action of Aliquat 336 on the steel surface.