Electrochemical and Computational Insights on the Application of Expired Metformin Drug as a Novel Inhibitor for the Sweet Corrosion of C1018 Steel.

An expired metformin drug (MET) was used as a corrosion inhibitor for C1018 carbon steel in a CO2-saturated 3.5 wt % NaCl + 340 ppm acetic acid solution under static conditions. The inhibitor was evaluated using electrochemical methods complemented with surface analytical measurements and computational modeling. The drug displayed a high inhibition efficiency of ∼90% at 200 ppm. Impedance analyses revealed a rise in the charge transfer resistance at the steel-solution interface upon the addition of the inhibitor. Polarization measurements suggested that MET acted more like a cathodic-type corrosion inhibitor and significantly reduced the corrosion current density. The adsorption of MET on the steel substrate followed the Langmuir isotherm, showing a mixed type of physical and chemical modes of adsorption. The thermodynamic parameters revealed strong and spontaneous adsorption on the steel surface. The surface analysis using SEM supported the inhibitor adsorption on the steel substrate. Based on the DFT simulation, inhibition by MET is mainly achieved by its protonated form, which leads to the formation of a thin film on the steel surface rather than the modification of the work function of the steel surface. The experimental and theoretical estimations of pKa complemented the DFT results, both agreeing that the monoprotonated form of MET is the dominant form in which the inhibitor adsorbs on the steel surface to form a thin film rather than modify the work function of the steel surface.

Cinnamaldehyde-modified chitosan as a bio-derived corrosion inhibitor for acid pickling of copper: Microwave synthesis, experimental and computational study.

Chitosan (CS) was cross-linked using cinnamaldehyde (Cinn) in a single step procedure following microwave irradiation to produce cinnamaldehyde-modified chitosan (Cinn-CS). The synthesized Cinn-CS was used as a novel corrosion inhibitor for copper in 1 M hydrochloric acid. A comprehensive electrochemical investigation using the impedance measurements, and potentiodynamic polarization was undertaken, supported with surface analysis and computational studies. The inhibitor Cinn-CS functioned by adsorption on the copper surface and showed an inhibition efficiency of >89% at a dose of 1000 mgL-1. The charge transfer resistance showed a rise with increase in inhibitor dosage to the corrosive medium, and the corrosion currents showed a significant decrease with the addition of the inhibitor. The Cinn-CS displayed a mixed type of inhibition performance with cathodic nature. The study of the copper surface using scanning electron microscopy depicted a considerably smooth morphology in the presence of the adsorbed Cinn-CS. The computational studies indicated that the Cinn-CS Schiff base shows better adsorption behavior compared to the parent molecules of chitosan and cinnamaldehyde and can show an inhibition performance in the neutral, and the protonated form.

Chitosan-cinnamaldehyde Schiff base: A bioinspired macromolecule as corrosion inhibitor for oil and gas industry.

A Schiff base of chitosan with cinnamaldehyde (Cinn-Cht) was synthesized in a single step using microwave irradiation and characterized using spectroscopic techniques. The synthesized Schiff base was used for the mitigation of carbon steel corrosion in 15% HCl. The corrosion evaluation was performed using weight loss tests, electrochemical impedance measurements, and polarization studies. The corrosion inhibition efficiency increased with inhibitor dosage and achieved a high value of 85.16% at 400 mgL-1. The inhibitor adsorption followed the Langmuir isotherm and displayed a mixed physical and chemical adsorption behavior. To further improve the corrosion inhibition efficiency, potassium iodide (KI) was incorporated in the corrosive solution, which increased the inhibition efficiency further to 92.45% at a concentration of 10 mM. Surface studies carried out via SEM analyses indicated the inhibitor adsorption and protective film formation on the steel surface. The computational studies carried out via DFT revealed that mainly the protonated form of inhibitor adsorbs on the metal surface. Monte Carlo simulation studies also showed that the protonated form of the inhibitor molecule exhibited higher adsorption energy than the neutral inhibitor.

Microwave-assisted synthesis of a new Piperonal-Chitosan Schiff base as a bio-inspired corrosion inhibitor for oil-well acidizing.

A new Schiff base of chitosan, namely Piperonal-chitosan (Pip-Cht), was synthesized for the first time, using a microwave irradiation method and characterized using spectroscopic techniques. The corrosion inhibition behavior of the new Schiff base was evaluated on carbon steel in 15% HCl medium via gravimetric and electrochemical techniques. This is the first work on the application of chemically functionalized chitosan as a corrosion inhibitor in the oil-well acidizing environment. The Pip-Cht inhibitor exhibited a high corrosion inhibition efficiency of 85.16% at a moderate dose of 600 mg L-1. Further, the addition of potassium iodide as a synergistic agent to the corrosive electrolyte produced a significant improvement in the inhibition efficiency to 91.15% at a low dosage of 10 mM of KI. At a higher temperature of 65 °C, the combination of both the inhibitor and KI yielded a high inhibition efficiency. The results of the gravimetric and electrochemical experiments were corroborated using AFM and SEM studies. The DFT calculations indicated that corrosion inhibition behavior of the Schiff base mainly occurs in the protonated form.

Aminotriazolethiol-functionalized chitosan as a macromolecule-based bioinspired corrosion inhibitor for surface protection of stainless steel in 3.5% NaCl.

Chitosan was chemically functionalized using aminotriazolethiol in a facile single-step synthesis. The macromolecule was evaluated as an inhibitor for corrosion of stainless steel in 3.5% NaCl solution. A detailed electrochemical investigation employing electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) was performed, which showed that the inhibitor acts by adsorption on the steel surface and shows a mixed type behavior with the prevalence of cathodic behavior. The new inhibitor aminotriazolethiol-modified chitosan (ATT-Cht) exhibited excellent water solubility and behaved as an efficient inhibitor against corrosion of stainless steel in 3.5% NaCl showing a corrosion inhibition efficiency of 97.8% at a concentration as low as 100 mg L-1. The results of surface studies using scanning electron microscopy along with energy dispersive X-ray spectroscopy supported the adsorption of the inhibitor on the steel surface.

Bis(2-aminoethyl)amine-modified graphene oxide nanoemulsion for carbon steel protection in 15% HCl: Effect of temperature and synergism with iodide ions.

HYPOTHESIS: There is a scarcity of available literature studies on the inhibition of aqueous corrosion using graphene and graphene oxide (GO) due to their poor aqueous solubility. The abundance of oxygen-containing functional groups on the surface of GO offers promising aspects for its chemical modification. Accordingly, we herein report the application of bis(2-aminoethyl)amine-modified graphene oxide (B2AA-GO) as a corrosion inhibitor for carbon steel in industrial oil-well acidizing conditions. EXPERIMENTS: B2AA was used to modify the graphene oxide (GO) chemically and characterized using FTIR, SEM, and TEM. The corrosion evaluations were undertaken in 15% HCl using weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization techniques supported by a thorough surface analysis using water contact angle measurements, FTIR, and atomic force microscopy. FINDINGS: It observed that the B2AA-GO acted by adsorption on the metal surface and exhibited a mixed type of nature with cathodic prevalence. The results showed that the chemically modified GO exhibits excellent inhibition behavior showing 90.27% corrosion inhibition efficiency up to 65 °C. Furthermore, iodide ions were introduced to improve the inhibition efficiency of the GO via synergistic action and inhibition efficiency of 96.77% was obtained at 65 °C. The obtained results show that the chemically modified GO is a promising corrosion inhibitor in the acidizing environment.

The synergistic influence of polyethyleneimine-grafted graphene oxide and iodide for the protection of steel in acidizing conditions.

Herein, graphene oxide (GO) was chemically functionalized with polyethyleneimine (PEI) in a single step to obtain PEI-GO, which was characterized via FTIR spectroscopy, SEM, and TEM. Additionally, for the first time, PEI-GO was employed for the corrosion mitigation of carbon steel in a solution of 15% HCl. The corrosion performance of the inhibitor was evaluated by utilizing weight loss tests, electrochemical measurements with impedance analysis, electrochemical frequency modulation, and potentiodynamic polarization studies. Thorough surface analysis was performed using 3D profilometry and static water contact angle measurements. PEI-GO was adsorbed on the steel surface and showed mixed-type corrosion inhibition behavior with the prevalence of cathodic characteristics. Additionally, potassium iodide was incorporated in the acid solution as a synergistic agent to enhance the corrosion inhibition behavior of PEI-GO. The obtained results showed that PEI-GO alone provided a high corrosion inhibition efficiency of 88.24% at a temperature of 65 °C and in the presence of KI, it showed an I.E. of 95.77% due to their synergistic effect. These interesting results demonstrate that PEI-GO can act as a potential corrosion inhibitor in acidizing conditions. The DFT-based computational studies showed that the inhibitor functioned in both its neutral and protonated forms.

Chitosan Schiff base: an environmentally benign biological macromolecule as a new corrosion inhibitor for oil & gas industries.

An eco-friendly Schiff base, namely Salicylaldeyde-Chitosan Schiff Base (SCSB), was synthesized by the reaction of chitosan and salicylaldehyde. In 3.5% NaCl saturated with carbon dioxide at 65 °C corrosion inhibition effect was analyzed using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods. The PDP results revealed that SCSB acts as a mixed type inhibitor and reduces the corrosion process effectively at 150 mg L-1 concentration with an inhibition efficiency of 95.2% and corrosion rate of 0.444 mm/y. EIS measurements suggest that the corrosion inhibition process is kinetically controlled. Langmuir adsorption model is the best fit among the other tested isotherms. The surface analysis was carried out using scanning electron microscopy (SEM), atomic force microscopy (AFM), scanning Kelvin probe (SKP), and X-ray photoelectron spectroscopy (XPS) to corroborate the formation of inhibitor film on the metal surface. Computational studies showed the effective adsorption of the protonated form of inhibitor.

Comprehensive investigation of steel corrosion inhibition at macro/micro level by ecofriendly green corrosion inhibitor in 15% HCl medium.

HYPOTHESIS: In the present time, there is enormous need for environmentally friendly and effective corrosion inhibitor for the acidizing process. During acidization 15% hydrochloric acid is used, which causes corrosion of N80 steel. EXPERIMENTS: The present study aims at the synthesis of environmentally benign corrosion inhibitor, namely 2-amino-4-(5-hydroxy-3-methyl-1H-pyrazole-4-yl)-4H-chromene-3-carbonitrile (PCP), and corrosion inhibition evaluation for N80 steel in 15% HCl. The inhibition potential of PCP was examined by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), density functional theory (DFT), and molecular dynamics simulation (MSD). The surface morphology of N80 steel samples was characterized by atomic force microscopy (AFM), contact angle measurement, UV-vis spectroscopy, and scanning electron microscopy (SEM). FINDINGS: The EIS measurements disclosed that PCP inhibits corrosion via kinetic controlled process. PDP results confirmed that PCP is a mixed type inhibitor and reduces the corrosion process effectively at 400 mg/L concentration with 98.4% efficiency. The adsorption of PCP followed Langmuir isotherm. Surface analysis by SEM, AFM, contact angle measurement, and UV-vis spectroscopy supports PCP adsorption over the N80 steel surface. The DFT study explores the adsorption and reactive regions of the PCP molecules. The MSD reveals that the diffusion co-efficient of the corrosive species in inhibited solution is less as compared to uninhibited.

Triazole-modified chitosan: a biomacromolecule as a new environmentally benign corrosion inhibitor for carbon steel in a hydrochloric acid solution.

In this work, a new inhibitor, triazole modified chitosan, was synthesized for the first time following chemical modification of chitosan using 4-amino-5-methyl-1,2,4-triazole-3-thiol. The newly synthesized biopolymer (CS-AMT) was characterized using FTIR and NMR, and then it was evaluated as an inhibitor against corrosion of carbon steel in 1 M hydrochloric acid. The corrosion testing and evaluation were performed thoroughly employing the weight loss method, electrochemical measurements and surface analysis. A maximum corrosion inhibition efficiency of >95% was obtained at 200 mg L-1 concentration of inhibitor. The adsorption of inhibitor obeyed the Langmuir isotherm and showed physical and chemical adsorption. The electrochemical study via impedance analysis supported the adsorption of the inhibitor on the surface of carbon steel, and the potentiodynamic polarization indicated a mixed type of inhibitor behavior with cathodic predominance. To get a better insight on the interaction of inhibitor molecules with the metal surface, a detailed theoretical study was performed using DFT calculations, Fukui indices analysis and molecular dynamics (MD) simulation. The DFT study showed a lower energy gap of CS-AMT and the MD simulations showed an increased binding energy of CS-AMT compared to the parent chitosan and triazole moieties thereby supporting the experimental findings.

Chitosan polymer as a green corrosion inhibitor for copper in sulfide-containing synthetic seawater.

The influence of chitosan on the copper corrosion in sulfide polluted synthetic seawater (SSW) containing 20 ppm of sulfide has been investigated for the first time. Potentiodynamic polarization measurements, electrochemical impedance spectroscopy at the open circuit potential and weight loss measurements were employed to assess the corrosion inhibition ability of chitosan. The impedance studies revealed that in the presence of chitosan at various concentrations, the charge transfer resistance increases. At a concentration of 800 ppm, chitosan exhibited a corrosion inhibition efficiency of 89% following physical adsorption. The influence of temperature and immersion time was studied in sulfide-contaminated synthetic seawater and significant inhibition was observed even after 90 days. SEM-EDS studies confirm the absence of the deterioration products on copper surface.

Thiosemicarbazide and thiocarbohydrazide functionalized chitosan as ecofriendly corrosion inhibitors for carbon steel in hydrochloric acid solution.

Organically functionalized chitosan macromolecules namely Chitosan-Thiosemicarbazide (CS-TS) and Chitosan-Thiocarbohydrazide (CS-TCH) were synthesized and evaluated as new corrosion inhibitors for mild steel corrosion in 1M HCl. The FTIR and 1H NMR studies confirmed the formation of the derivatives. The corrosion tests were performed using weight loss method, electrochemical measurements, surface morphology (AFM), quantum chemical investigation and molecular dynamics simulation methods. The maximum efficiency of 92% was obtained at a concentration as low as 200mgL-1. The inhibitors were found to obey Langmuir adsorption isotherm and exhibited both physical and chemical adsorption. Electrochemical impedance spectroscopy (EIS) results showed an increase in polarization resistance which supported the adsorption of inhibitors on the mild steel surface. Tafel data showed a mixed type behavior with cathodic predominance. The data of quantum chemical calculations and molecular dynamics simulation supported the experimental findings.

Role of nanostructured networks as analytical tools for biological systems.

In recent years, nanostructured materials have emerged as potential candidates offering excellent prospects for interfacing the detection of biomolecules. Nanomaterials such as nanoparticles, nanostructured silicates, nano-sized metal oxides, nanostructured polymers, quantum dots, nanocomposites and sensing nanodevices are being utilized worldwide for fabrication of chemical sensors and sensor arrays with tailored characteristics and tuneable properties. Among above, the materials that create a matrix structure at the nanoscale level are particularly fascinating. The exceptional physical, chemical, mechanical and electrical properties of these matrices advocate their application in the electrode modification resulting in sensing devices and transducers with superior performance. Here we present an overview of different types of nanostructured networks that are applied in sensor development. The role of these materials in chemical sensors is described along with the techniques that are the backbone of the sensing process. Special attention has been given to some key sensors that are directly related to human physiology and have clinical significance.

3-Glycidoxypropyltrimethoxysilane mediated in situ synthesis of noble metal nanoparticles: application to hydrogen peroxide sensing.

The in situ synthesis is reported of noble metal nanoparticles via 3-glycidoxypropyltrimethoxysilane mediated reduction of 3-aminopropyltrimethoxysilane treated metal salts during sol-gel processing. The method described involves the synthesis of uniform spherical nanoparticles of gold, silver and palladium with controlled size that can be directly utilized for thin film preparation. A detailed study of the synthesis and application of gold nanoparticles to the electrochemical detection of hydrogen peroxide was carried out and reveals that the amplification of hydrogen peroxide sensing is size-dependent. In addition, these nanoparticles exhibit excellent compatibility towards composite preparation. As an example, a nanocomposite with Prussian Blue (PB) is synthesized and found to be useful for the fabrication of chemically modified electrodes (CME). The resulting CME shows dramatic improvement in the electrochemistry of PB with gradual enhancement in electrocatalytic efficiency towards hydrogen peroxide sensing. The nanocomposite is used to study the direct and horseradish peroxidase (HRP)-catalyzed reduction of hydrogen peroxide. The results recorded for hydrogen peroxide analysis show an improvement in sensitivity and limit of detection on decreasing the size of gold nanoparticles in all cases.