M.A. Quraishi

Electrochemical behavior of steel/acid interface: adsorption and inhibition effect of oligomeric aniline

The present work shows the development of new protective oligomeric aniline (O-ANI) and its effect on electrochemical corrosion behavior of low carbon steel (LCS) in 1 M HCl at 308 K. The synthesized O-ANI was subjected to spectroscopic and electrochemical characterizations. The inhibition of LCS corrosion by O-ANI was studied using open circuit potential (OCP), potentiodynamic polarization (PDP), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. The potentiodynamic polarization data indicated that O-ANI suppresses predominantly the cathodic process of corrosion reaction in comparison to the anodic process. The inhibition efficiency of the O-ANI depends on the length of the oligomeric chain and position of the functional groups. The spectra of all elements, within limits, on the steel surface was determined by energy-dispersive X-ray spectroscopy (EDX). Morphological changes on the electrode surface were monitored by scanning electron microscopy (SEM). The thermodynamic parameters such as the adsorption equilibrium constant (Kads) and the free energy of adsorption (ΔG°ads) were calculated and discussed. Several adsorption isotherms were tested and the experimental data fitted well with the Langmuir adsorption isotherm. UV-visible spectral analysis of O-ANI solution containing LCS indicates the formation of Fe–N (ligand–metal) charge-transfer complex type interaction.

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.

Corrosion inhibition of N80 steel in 15% HCl by pyrazolone derivatives: electrochemical, surface and quantum chemical studies

The corrosion protection of N80 steel in 15% HCl by two pyrazolone derivatives namely 2-(3-amino-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)(p-tolyl)methyl)malononitrile (PZ-1) and 2-((3-amino-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)(phenyl)methyl)malononitrile (PZ-2) has been investigated by using gravimetric, electrochemical and quantum chemical studies. The observed results reveal that PZ-1 is a better inhibitor than PZ-2. Tafel polarization showed that PZs are mixed type inhibitors but dominantly affect the cathodic reaction. Both inhibitors were found to obey the Langmuir adsorption isotherm. Scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) images support the protection of the N80 steel in the presence of the PZs. Quantum chemical study reveals that both inhibitors have a tendency to get protonated and this result supports the experimental observations.

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.

Some Pyrimidine Derivatives as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid

The inhibition effect of four pyrimidine derivatives (PPDs) on the corrosion of mild steel in hydrochloric acid medium has been investigated using gravimetric measurements, electrochemical impedance spectroscopy, potentiodynamic polarization, and energy dispersive x-ray spectroscopy (EDX) techniques. Electrochemical impedance spectroscopy (EIS) data showed that the addition of PPDs increases the charge-transfer resistance (Rct) and decreases the double-layer capacitance (Cdl). Potentiodynamic polarization revealed that PPDs acted as mixed-type inhibitors but are predominantly cathodic. The adsorption of studied compounds obeyed the Langmuirs adsorption isotherm. EDX and quantum chemical calculations support the experimental results. GRAPHICAL ABSTRACT