Mixed-type Inhibitor Research Articles

Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L−1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV–vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

Preparation of corrosion inhibitor from natural plant for mild stil immersed in an acidic environmental: experimental and theoretical study

In the present study, the inhibition performance of some medicinal plants (i.e. Yarrow, Wormwood, Maurorum, Marjoram, and Ribes rubrum) was theoretically and experimentally investigated for mild steel immersed in 1M HCl. In this way, the obtained extracts characterized by Fourier transform infrared spectroscopy (FT-IR) and the electrochemical and theoretical techniques were used to study the inhibition mechanisms of the extracts for the immersed electrode in the acidic solution. In addition, the microstructure of the electrode surface immersed in the blank and inhibitor-containing solutions characterized by field emission scanning electron microscopy (FE-SEM), and Violet-visible (UV–Vis) spectroscopy was used to confirm the adsorption of the compounds on the electrode surface. The obtained electrochemical results revealed that the inhibition performance of the green inhibitors increased by increasing their dosage in the electrolyte. In addition, it was proved that Marjoram plant extract possessed the most inhibition efficiency (up to 92%) among the under-studied herbal extracts. Marjoram extract behaved as a mixed-type inhibitor in the hydrochloric acid solution, and the adsorption process of the extract on the steel surface followed the Langmuir adsorption model. Adsorption of the compounds on the steel surface was also studied using density functional theory (DFT), and it was found that the protonated organic compounds in the extract have a high affinity for adsorption on the electrode surface in the acidic solution.

Electropolymerized conducting polyaniline coating on nickel-aluminum bronze alloy for improved corrosion resistance in marine environment

Corrosion of metals in marine environments is a vital problem with significant negative economic impacts and coating is an effective measure of protection. In this work, polyaniline (PANI) conducting polymer was deposited as a protective layer on a nickel-aluminiumbronze (NAB) alloy using the galvanostatic electropolymerization method at different current densities. The deposited coating was characterized by various techniques such as FTIR and SEM. To evaluate its effectiveness in corrosion protection, the anticorrosion properties of different PANI coatings were evaluated in a 3.5 wt% NaCl solution by both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical results revealed that PANI coatings acted as a barrier towards the corrosive species and provided significant corrosion resistance to NAB degradation, with an inhibition efficiency of about 93% and a mixed-type inhibition behavior with cathodic predominance. Furthermore, corrosion protection was found to be dependent on the coated film properties and the optimum corrosion inhibition was achieved under the test conditions for films deposited at a current density of 5 mA cm-². Moreover, Raman spectroscopy confirmed the presence of the partially oxidized conductive polyaniline, the emeraldine form and its polaron structure, on the alloy surface. In addition, atomic force microscopy (AFM) was used to monitor the changes in the microstructure of the coating after exposure to the saline environment and demonstrated the formation of a robust coating with a significantly lower (5 times) surface roughness for the coated alloy than the uncoated surface after immersion. Overall results strongly support the potential of PANI for corrosion protection of the NAB alloy.

Novel high-performance and cost-effective green inhibitor based on fundamental theoretical evaluations combined with electrochemical/surface examinations of Arachis hypogaea shell extract for pipeline steel corrosion in 1 M H2SO4 solution

Traditional corrosion inhibitors have been frequently used for metal protection against strong acids. However, most of them are hazardous compounds with high costs. Therefore, due to the strict environmentally friendly regulations, green and low-cost compounds from renewable sources have gained high consideration in recent applications. In the present study, the Arachis hypogaea shell extract, commonly called groundnut, a cost-effective was selected to inhibit API X 65 pipeline steel corrosion in 1 mol·L−1 H2SO4 solution. The Arachis hypogaea shell composition was examined by FTIR analysis. The Arachis hypogaea shell on pipeline steel in H2SO4 solutions was studied via gravimetric, potentiodynamic polarization, and surface analysis (SEM and EDX). Electron donor atoms present in the Arachis hypogaea shell extract molecules is responsible for its adsorption on the surface of the metal. Experimental study shows that with increasing Arachis hypogaea shell concentrations, the inhibition tendency increased and reached 98.84% at 4 g L−1 after 24 h. Arachis hypogaea shell extract behaved as mixed-type inhibitor, and the surface coverage fits the Langmuir isotherm, signifying that the steel surface was covered by a monolayer of inhibitor molecules without intermolecular interactions. SEM analysis shows that Arachis hypogaea molecule adsorption on the metal surface reduced considerably its dissolution rate resulting in a smooth and clean surface with few damaged areas. The use of water for extraction of Arachis hypogaea shell exhibiting inhibition efficiency, non-toxic, and cost-effective than other green inhibitors, proposes the Arachis hypogaea shell as an excellent green inhibitor for API X 65 steel corrosion in 1 mol·L−1 H2SO4 solution.

Structure-based inhibition of acetylcholinesterase and butyrylcholinesterase with 2-Aryl-6-carboxamide benzoxazole derivatives: synthesis, enzymatic assay, and in silico studies.

An important research topic is the discovery of multifunctional compounds targeting different disease-causing components. This research aimed to design and synthesize a series of 2-aryl-6-carboxamide benzoxazole derivatives that inhibit cholinesterases on both the peripheral anionic and catalytic anionic sides. Compounds (7-48) were prepared from 4-amino-3-hydroxybenzoic acid in three steps. The Ellman test, molecular docking with Maestro, and molecular dynamics simulation studies with Desmond were done (Schrodinger, 12.8.117). Compound 36, the most potent compound among the 42 new compounds synthesized, had an inhibitory concentration of IC50 12.62 nM for AChE and IC50 25.45 nM for BChE (whereas donepezil was 69.3 nM and 63.0 nM, respectively). Additionally, compound 36 had docking values ​​of - 7.29kcal/mol for AChE and - 6.71kcal/mol for BChE (whereas donepezil was - 6.49kcal/mol and - 5.057kcal/mol, respectively). Furthermore, molecular dynamics simulations revealed that compound 36 is stable in the active gorges of both AChE (average RMSD: 1.98 Å) and BChE (average RMSD: 2.2 Å) (donepezil had average RMSD: 1.65 Å and 2.7 Å, respectively). The results show that compound 36 is a potent, selective, mixed-type dual inhibitor of both acetylcholinesterase and butyrylcholinesterase. It does this by binding to both the catalytically active and peripheral anionic sites of cholinesterases at the same time. These findings show that target compounds may be useful for establishing the structural basis for new anti-Alzheimer agents.

Enhancing steel corrosion resistance in 1.0 M HCl medium through the synthesized and characterized mixed pyrophosphates BMnP2O7 (B = Ni, Co, and Cd)

In this study, we synthesized three diphosphate materials NiMnP2O7, CoMnP2O7, and CdMnP2O7 intended for use as corrosion inhibitors for carbon steel. The crystallinity of the obtained compounds was analyzed using X-ray diffraction (XRD), and a vibrational analysis was carried out by infrared (IR) and Raman (Ra). The corrosion inhibition properties of steel with these materials in 1.0 M HCl solution were investigated using three important techniques. The electrochemical parameters were obtained via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP) and the surface of the substrate was analyzed, using the scanning electron microscopy (SEM). Our findings indicate that the optimal concentration for NiMnP2O7, CoMnP2O7, and CdMnP2O7 was 10−3 mol/L, with inhibition efficiencies reaching to 87.5 %, 91.04 %, and 92.22 %, respectively. These phosphates also act as a mixed-type inhibitors, imparting high resistance to corrosion, and their inhibition efficiency (η%) increased with the augmentation of the inhibitor concentration. The scanning electron microcopy (SEM) images revealed that the inhibitors form a protective layer against acid attack, preventing carbon steel from being destroyed.

A new Corrosion Inhibitor Based on Modification of Polyacrylic acid in acidic Solution

This search investigates the corrosion inhibition properties of polyacrylic acid. The corrosion inhibition performance of carbon steel (CS) in a 1M HCl solution treated with the polyacrylic acid inhibitor was evaluated using potentiodynamic polarization measurement, Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The findings of this study demonstrate that polyacrylic acid exhibits significant effectiveness as corrosion inhibitor for CS in Acid solution. The inhibitor acts as a mixed-type inhibitor, and its corrosion inhibition efficiency increases with higher concentrations of polyacrylic Acid concentration up to 89.9% obtained at 298 K for a 400 ppm concentration, while decreasing with increasing acid concentration.

Chemometric guided isolation of new triterpenoid saponins as acetylcholinesterase inhibitors from seeds of Achyranthes bidentata Blume

Achyranthes bidentata Blume (Amaranthaceae) is an annual or perennial herb widely used as ethnomedicine in Traditional Chinese Medicine for treating fever, cold, ulcers, mensural pain, dementia, and osteoporosis. In the current study, UPLC-IM-Q-TOF-MS/MS-based chemometric approach was adopted for the tentative identification of fifty-six compounds in the extract and fractions of A.bidentata seeds. Further, the chemometric-guided isolation led to the isolation of two previously undescribed oleanane-type triterpenoid saponins, named achyranosides A-B (27 and 30), along with three known compounds (31, 44, and 23) from water fraction of A. bidentata seeds. The structures of new compounds were elucidated based on the detailed analysis of NMR, HR-ESI-MS, FT-IR spectral data, and GC-FID techniques. The isolated compounds in vitro acetylcholinesterase inhibitory activity revealed the promising activity of chikusetsusaponin IVa (23) (IC50 = 63.7 μM) with mixed type of AChE inhibition in enzyme kinetic studies. Additionally, in silico binding free energy of isolated compounds disclosed the greater stability of enzyme-ligand complex owing to underlying multiple H-bond interactions. Overall, the study demonstrates the effectiveness of a chemometric-guided approach for the phytochemical exploration and isolation of new oleanane-type triterpenoid saponins from A. bidentata seeds.

Corrosion inhibition performance of new Schiff base cyclohexanamine derivatives on C-steel in 1 M HCl solution: Electrochemical, chemical, surface and computational explorations

Iron has many advantages, which makes it a material of great importance on the industrial level, but it is quickly affected by surrounding environmental factors that cause its corrosion. In this context, two new Schiff base cyclohexanamine derivatives (CSBs) were synthesized, characterized, and screened as corrosion inhibitors of C-steel in a 1 M hydrochloric acid solution. Specifically, they are (Z)-N-cyclohexyl-1-phenylethan-1-imine (CSB-1) and (E)-N′-cyclohexyl-N-hydroxybenzimidamide (CSB-2). 1H NMR was used to determine the structures of the new CSB molecules. The inhibition efficacies (%IE) were evaluated by combining theoretical, physical, chemical, electrochemical, and spectroscopic methods. The results confirmed that CSBs were mixed-type inhibitors and that the IE depended linearly on their concentration. The adsorption of these molecules on the metal surface is key to this role. Kinetic and thermodynamic studies indicated that they are physically adsorbed and subject the Langmuir adsorption isotherm. Using 0.001 M of inhibitor, the maximum %IEs achieved were 91.1 % for CSB-1 and 94.4 % for CSB-2, respectively, which confirms tatehat they are promising inhibitors. Surface analysis via atomic force microscopy (AFM) confirmed that the C-steel was covered in a protective layer. Several thermodynamic and kinetic parameters were calculated. DFT and Mullikan charge calculations and molecular dynamics (MD) simulations were applied to predict the effectiveness and interactions of new CSBs on the steel surface as well. Theoretical expectations correspond to the practical.

Eco-friendly methanolic Ajuga orientalis extract as corrosion inhibitor for aluminium in 1.0 M NaOH

The inhibitory impact of the methanolic Ajuga orientalis (MAO) extract on Al corrosion in 1.0 M NaOH solution was examined using weight loss with electrochemical polarisation and scanning electron microscopy (SEM) techniques. According to the findings, the extract was an effective inhibitor in basic condition, as well as inhibition effectiveness increased with concentration. Furthermore, temperature studies revealed a loss in efficiency followed by a rise when temperature rose, followed by an increase and a fall in the fundamental media when the temperature increased from 30 °C to 50 °C. Frumkin, Freundlich and El Awady isotherms were used to mimic the inhibitor's adsorption properties. For the inhibitory behaviour, physical and chemical adsorption mechanisms are proposed. The adsorption process's thermodynamic parameters (ΔH*, ΔS* and Ea) were determined and explained. The inhibitor was examined as a mixed-type (anodic and cathodic) inhibitor based on polarisation studies. The inhibitor, according to the SEM data, is partially coating the metal surface, providing it with a reasonable amount of protection. The findings from weight loss, electrochemical polarisation, SEM and quantum chemical calculations collectively demonstrate a strong consensus, indicating that the MAO extract exhibits high effectiveness as an inhibitor for aluminium in a basic solution.

A convolutional neural network -VGG16 method for corrosion inhibition of 304SS in sulfuric acid solution by timoho leaf extract

A corrosion inhibition test, coupled with a quantification of in-situ H2 evolution, can be used to evaluate an organic inhibitor such as Timoho leaf extract (TLE). TLE is a biodegradable and effective corrosion inhibitor because of its potential to protect 304SS against sulfuric acid. TLE corrosion inhibitor was studied through systematic electrochemical experiments and morphological characterization, with a concentration range of 0–6g L−1. Convolutional Neural Network (CNN)-VGG16 was one of the machine learning approaches used to classify and predict physical changes in hydrogen gas bubbles. Constituents of the TLE and 304SS surfaces were analyzed by FT-IR and UV–Vis tests. The results suggested that 3 g L−1 TLE inhibitor was able to reduce the corrosion rate by 99.37 %. The TLE's inhibition mechanism on 304SS was mixed adsorption and mixed type inhibitor that followed the Isothermal Freundlich Equation. The prediction model by CNN-VGG16 for corrosion tests at varied inhibitor doses was 96% accurate. SEM tests revealed that TLE constituent adsorption on the 304SS surface had a smooth surface morphology with few degraded spots.

Novel 6-alkyl-bridged 4-arylalkylpiperazin-1-yl derivatives of azepino[4,3-b]indol-1(2H)-one as potent BChE-selective inhibitors showing protective effects against neurodegenerative insults

Due to the putative role of butyrylcholinesterase (BChE) in regulation of acetylcholine levels and functions in the late stages of the Alzheimer's disease (AD), the potential of selective inhibitors (BChEIs) has been envisaged as an alternative to administration of acetylcholinesterase inhibitors (AChEIs). Starting from our recent findings, herein the synthesis and in vitro evaluation of cholinesterase (ChE) inhibition of a novel series of some twenty 3,4,5,6-tetrahydroazepino[4,3-b]indol-1(2H)-one derivatives, bearing at the indole nitrogen diverse alkyl-bridged 4-arylalkylpiperazin-1-yl chains, are reported. The length of the spacers, as well as the type of arylalkyl group affected the enzyme inhibition potency and BChE/AChE selectivity. Two compounds, namely 14c (IC50 = 163 nM) and 14d (IC50 = 65 nM), bearing at the nitrogen atom in position 6 a n-pentyl- or n-heptyl-bridged 4-phenethylpiperazin-1-yl chains, respectively, proved to be highly potent mixed-type inhibitors of both equine and human BChE isoforms, showing more than two order magnitude of selectivity over AChE. The study of binding kinetics through surface plasmon resonance (SPR) highlighted differences in their BChE residence times (8 and 47 s for 14c and 14d, respectively). Moreover, 14c and 14d proved to hit other mechanisms known to trigger neurodegeneration underlying AD and other CNS disorders. Unlike 14c, compound 14d proved also capable of inhibiting by more than 60% the in vitro self-induced aggregation of neurotoxic amyloid-β (Aβ) peptide at 100 μM concentration. On the other hand, 14c was slightly better than 14d in counteracting, at 1 and 10 μM concentration, glutamate excitotoxicity, due to over-excitation of NMDA receptors, and hydrogen peroxide-induced oxidative stress assessed in neuroblastoma cell line SH-SY5Y. This paper is dedicated to Prof. Marcello Ferappi, former dean of the Faculty of Pharmacy of the University of Bari, in the occasion of his 90th birthday.

Fabrication of Protective Organic Layer Using Schiff-Base Metal Complex Responsible for Excellent Corrosion Performance: Experimental and Theoretical Perspectives.

The effectiveness of a copper(II) complex with a Schiff base derived from 2-amino-4-phenyl-5-methylthiazole and salicylaldehyde (APMS) as a corrosion inhibitor for XC18 steel in an HCl solution was investigated. Experimental findings indicated a slight negative correlation between inhibition efficiencies in 1 M HCl and temperature but a positive correlation with both inhibitor concentration and immersion time, respectively. The weight loss measurement revealed that APMS achieved a maximum inhibition rate of 92.07% at 303 K. A fitting analysis demonstrated that APMS adheres to the Langmuir adsorption isotherm. The electrochemical results revealed an enhanced inhibitive performance of APMS, with the efficiency increasing as concentrations increased, ultimately reaching a peak of 94.47% at 5 × 10-3 mol L-1. Potentiodynamic polarization measurements revealed that APMS acted as a mixed-type inhibitor without affecting the corrosion mechanism. Scanning electron microscopy investigations of the metal surfaces corroborated the presence of an adsorbed organic layer. Advanced theoretical calculations utilizing density functional theory and first-principles density-functional tight-binding were conducted to gain insights into the behavior of APMS on the metal surface. APMS derives its advantages from crucial inter- and intramolecular interactions, resulting in the formation of a resilient adsorption layer, in line with the experimental findings. It is found that the presence of the APMS-based inhibitor exhibits a significant synergistic corrosion inhibition effect. The current study offers a design direction for enhancing the structural characteristics of Schiff base metal complexes, laying the groundwork for multifunctional frameworks to minimize corrosion rates with considerations for real-world use and cost-efficiency. The ability to replace harmful, expensive constituents with sustainable, and cost-effective organic alternatives represents a significant outcome of this study.

Design of New Ecofriendly Schiff Base Inhibitors for Carbon Steel Corrosion Protection in Acidic Solutions: Electrochemical, Surface, and Theoretical Studies.

Corrosion poses a significant problem for several industrial sectors, inducing continuous research and development of corrosion inhibitors for use across a wide range of industrial applications. Here, we report the effectiveness of three newly developed Schiff bases derived from amino acids and 4-aminoacetophenone, namely, AIP, AMB, and AImP, as environmentally friendly corrosion inhibitors for Q235 steel in hydrochloric acid using electrochemical and surface analyses, in addition to theoretical techniques. The electrochemical findings of potentiodynamic polarization (PDP) demonstrated that the explored compounds serve as mixed-type inhibitors and can effectively suppress steel corrosion, with maximal protection efficiencies of 93.15, 96.01, and 77.03% in the presence of AIP, AMB, and AImP, respectively, at a concentration of 10 mM. The electrochemical impedance spectroscopy (EIS) and polarization results confirmed the growth of a durable protective barrier on the steel surface in the existence of the inhibitors, which is responsible for decreasing the metallic dissolution. Results were further supported by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis, and Fourier transform infrared (FTIR), which ascribed the development of inhibitor-adsorption films on the steel surface. The results of EDS and XPS analyses demonstrated the existence of the distinctive elements of the inhibitors on the metallic surface. Furthermore, density functional theory (DFT) calculations and Monte Carlo (MC) simulations showed the electronic structure of the examined inhibitors and their optimized adsorption configurations on the steel surface, which helped in explaining the anticorrosion mechanism. Finally, the theoretical and experimental findings exhibit a high degree of consistency.

Insights of 2-(Benzoxazol-2-ylthio)-N-(4-phenyl-5-phenylazo-thiazol-2-yl)-acetamide as a novel corrosion inhibitor for J55 carbon steel in hydrochloric acid: Experimental, Spectroscopic analysis, and theoretical studies

The inhibitory efficacy of 2-(Benzoxazol-2-ylthio)-N-(4-phenyl-5-phenylazo-thiazol-2-yl)-acetamide (BNP) was systematically explored through weight loss measurements, potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS), in relation to the corrosion mitigation of J55 carbon steel (J55CS) within hydrochloric acid (HCl) environments. This research employs a combination of experimental techniques, including gravimetric analysis, electrochemical tests, and theoretical considerations. It has been determined that BNP has an inhibitory effect on the corrosion of J55CS in strong HCl, reaching 91.8% at 18 × 10−6 M at 298 K. The inhibitory efficiency displays a notable enhancement as the concentration of the BNP is elevated within the range of 3–18 × 10−6 M. Conversely, the IE% experiences a raised when the temperature is raised. This augmentation can be attributed to the inherent ability of BNP to facilitate the formation of inhibitory films on the surface of J55CS. An analysis of Tafel plots reveals that the BNP adheres to a mixed-type inhibitor. The adsorption of BNP obeyed the Temkin adsorption isotherm. The investigated isotherm plots revealed that the adsorption process for BNP on the metal surface was endothermic, spontaneous, and chemical adsorption. Theoretical modeling [density functional theory (DFT) and Monte Carlo (MC)] revealed the correlation between the BNP molecular chemical structure and its anticorrosive property.

Magnolol derivatives as specific and noncytotoxic inhibitors of breast cancer resistance protein (BCRP/ABCG2)

The breast cancer resistance protein (BCRP/ABCG2) transporter mediates the efflux of numerous antineoplastic drugs, playing a central role in multidrug resistance related to cancer. The absence of successful clinical trials using specific ABCG2 inhibitors reveals the urge to identify new compounds to attend this critical demand. In this work, a series of 13 magnolol derivatives was tested as ABCG2 inhibitors. Only two compounds, derivatives 10 and 11, showed partial and complete ABCG2 inhibitory effect, respectively. This inhibition was selective toward ABCG2, since none of the 13 compounds inhibited neither P-glycoprotein nor MRP1. Both inhibitors (10 and 11) were not transported by ABCG2 and demonstrated a low cytotoxic profile even at high concentrations (up to 100 µM). 11 emerged as the most promising compound of the series, considering the ratio between cytotoxicity (IG50) and ABCG2 inhibition potency (IC50), showing a therapeutic ratio (TR) higher than observed for 10 (10.5 versus 1.6, respectively). This derivative showed a substrate-independent and a mixed type of inhibition. The effect of compound 11 on the ABCG2 ATPase activity and thermostability revealed allosteric protein changes. This compound did not affect the expression levels of ABCG2 and increased the binding of the conformational-sensitive antibody 5D3. A docking study showed that 11 did not share the same binding site with ABCG2 substrate mitoxantrone. Finally, 11 could revert the chemoresistance to SN-38 mediated by ABCG2.

Potential anti-hyperglycemic activity of black tea theaflavins through inhibiting α-amylase

Hyperglycemia can cause early damage to human bady and develop into diabates that will severely threaten human healthy. The effectively clinical treatment of hyperglycemiais is by inhibiting the activity of α-amylase. Black tea has been reported to show inhibitory effect on α-amylase and can be used for hyperglycemia treatment. However, the mechanism underlying is unclear. In this study, in vivo experiment showed that black tea theaflavins extract (BTE) effectively alleviated hyperglycemia. In vitro experiment showed that the effects may be caused by the interation between theaflavins and α-amylase. While TF1 and TF3 were mixed type inhibitors of α-amylase, TF2A and TF2B were competitive inhibitors of α-amylase. Molecular docking analysis showed that theaflavins monomers interacted with the hydrophobic region of α-amylase. Further study verified that monomer-α-amylase complex was spontaneously formed depending on hydrophobic interactions. Taken together, theaflavins showed potential anti-hyperglycemia effect via inhibiting α-amylase activity. Our results suggested that theaflavins might be utilized as a new type of α-amylase inhibitor to prevent and cure hyperglycemia.

Inhibition of corrosion of mild steel in simulated oil well waterby aqueous extract of Hibiscus rosa-sinensis flower

controlling the corrosion of mild steel in simulated oil well water (SOWW). Weight loss method reveals that 10 % v/v of the extract offers 82 % inhibition efficiency (IE) to mild steel (MS) immersed SOWW. The mechanistic aspects of corrosion inhibitive effect have been investigated by polarization study and AC impedance spectra. Polarization study reveals that the mixed type of inhibitor in the presence of inhibitor system. The corrosion inhibition effect is confirmed by the increase in the linear polarization resistance value and decrease in the corrosion current value. The protective layer is formed on the metal surface is confirmed by the AC impedance spectra. This is confirmed by the fact that there is increase in charge transfer resistance value and decrease in the double layer capacitance value. The adsorption of inhibitor molecule obey Langmuir adsorption isotherm. The protective coating is characterized by FTIR spectroscopy. It confirms that the inhibitor has coordinated with ferrous ion the metal surface through the active principle component of β-sitosterol, quercetin and kaempferol-3-xylosylglucoside. The surface morphology has been investigated by scanning electron microscopy (SEM). Hence, aqueous extract of Hibiscus rosa-sinensis flower with simulated oil well water good corrosive inhibitive effect on pipeline made of mild steel.

Sustainability approach to corrosion mitigation using eco-friendly inhibitor for oil and gas applications

Investigation of Euphorbia hirta leaves as green corrosion inhibitor for mild steel in 0.5 M hydrochloric acid using gravimetric and potentiodynamic polarization techniques was carried out. Characterization carried out on the leaves were quantitative, qualitative analyses, Fourier Transform Infrared Spectroscopy (FT-IR), and Gas Chromatography-Mass Spectrometry (GC-MS). Scanning electron microscopy (SEM) attached with electron dispersive spectroscopy (EDS) was used to characterize the Substrates before and after corrosion tests. Both the inhibitor concentration, time, and temperature were varied accordingly. The corrosion rate increased with an increase in temperature and decreased with increases in both inhibitor concentrations and time. An inhibition efficiency of 98.32% recorded at the optimum concentration of 12 g/l. Phytochemical results revealed tannins, alkaloids, saponins, and flavonoids with their contents. FT-IR and GC–MS revealed some functional groups such as Aliphatic cyanide/nitrile, C=N, Primary amine, CN stretch, Aliphatic bromo compounds, C-Br stretch, 7,17 Hexadecadienal, etc which were responsible for the protection of mild steel in the acidic medium. The inhibition efficiency obtained suggested the effectiveness of the inhibitor and acted as a mixed-type inhibitor. The substrates without green inhibitors were rough with severe pits, while the surfaces with optimum green inhibitors were protected. The results obtained from weight loss, and polarization were in good agreement with each other. Green corrosion inhibitors can, therefore, serve as an alternative to synthetic. The inhibition efficiency obtained is well above the minimum acceptable limit of 70% required of a good inhibitor. It can be used in the formulation of paints for coating of pipes.

Computational Modelling and Comparative Analysis of aSchiff Base Ligand and Its Analog as Inhibitors Against Mild Steel Corrosion in 1M HCl

Schiff bases, alternative anticorrosive additive wassynthesized, characterized and investigated for the inhibition of mild steel corrosion in 1M Hydrochloric acid at concentrations of 20 ppm, 40 ppm, 60 ppm, 80 ppm and 100 ppm using weight loss (WL) and electrochemical methods. The novel Schiff base ligands obtained were characterized by Ultraviolet-visible and Fourier-Transform Infrared Spectroscopy. The elemental analysis data for the Schiff base ligands were used to confirm the general formula of the Schiff bases. Fourier-Transform Infrared spectroscopy provided evidence of formation of a complex surface film due to adsorption of the Schiff bases on the mild steel surface. Maximum inhibition efficiency for Schiff base ligand 1 (SBL1) and Schiff base ligand 2 (SBL2) obtained were respectively 76.92% and 86.21% at concentrationof100ppm,andthetrendfollowedSBL2>SBL1, indicating the effectiveness of SBL2 in corrosion prevention as compared SBL1. Potentiodynamic polarization(PDP) measurements showed that the Schiff bases acted as mixed type inhibitors. Electrochemical Impedance Spectroscopic (EIS) measurement revealed that the corrosion process was controlled by charge transfer process. Inhibition efficiency values obtained from the different techniques were comparable. Quantum chemical parameters such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital(LUMO) and energy gap (ΔE) were obtained using Hartree-fock Density Functional Theory by Hamiltonian method. The results showed that SBL2 was more reactive than SBL1. In conclusion, the inhibition of mild steel corrosion was due to adsorption of active molecules leading to formation of a protective layer on surface of mild steel.