Function Of Inhibitor Concentration Research Articles

Synthesis and Electrochemical Properties of Oleylamine as a Sour Saline Corrosion Inhibitor Under Laminar Flow at 40 °C.

In this study, the synthesis of a long-chain aliphatic amino compound and its sour corrosion inhibition properties were reported. Oleylamine was obtained through the reaction of 4-(Aminomethyl) pyridine with 1-chloro-octadecane. The identification and characterization of reaction products were carried out through Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectroscopy (GC-MS). Oleylamine was tested as a sour corrosion inhibitor for steels. Different concentrations of oleylamine (0, 5, 10, 25, and 100 ppm) in a sour saline electrolyte were analyzed. The dynamic anticorrosive behavior of oleylamine on carbon mild steel (AISI 1018) surfaces was evaluated using a laminar flow of 100 rpm and tested with potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. After electrochemical testing, the surface of the steel specimens that were used was characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The electrochemical results of the anticorrosive efficiency of oleylamine for steel showed an exponential behavior as a function of inhibitor concentration. At a concentration of 20 ppm of the inhibitor, the anticorrosive efficiency did not show any significant changes. However, at 100 ppm of the inhibitor, an efficiency of over 95% was achieved. After the electrochemical tests, the surface of the steel samples with the inhibitor revealed the formation of an inhibitor layer that prevented the corrosion of the steel.

Abstract 1666: A novel sox-based continuous and homogeneous assay for the discovery of inhibitors of inactive and active AKT

Abstract Introduction: The activity of protein kinases plays a critical role in the aberrant activation of oncogenic signaling pathways which can drive tumorigenesis and malignant transformation in cancer. AKT has been shown to be both upregulated and mutated in cancer cells allowing it to serve as a driver of cancer cell growth and progression. Inhibition of AKT activation and activity are both attractive targets for effective cancer drug discovery. Experimental Procedures: We developed continuous, homogeneous assays for unactive AKTs. A peptide substrate, modified with a sulfonamido-oxine fluorophore (Sox), utilizes chelation-enhanced fluorescence to enable a real-time readout of AKT-driven phosphorylation. First, a subset of 30,000 Sox-containing sequences were evaluated for AKT substrate candidates, selecting for assay robustness and specificity. A physiologically relevant peptide substrate was identified and used to develop a kinetic assay to monitor AKT1 activation and activity. Unactive AKT1 was incubated with DOPS/DOPC and PIP3, which mimics the plasma membrane, allowing the PH domain of AKT to bind, leading to a conformational change that enables full activation of AKT by PDK1 and MK2. Upon assay initiation, active AKT phosphorylates the sensor peptide, and the resulting signal is read in kinetic mode using a fluorescence intensity readout. First derivative plots for each progress curve were generated; the slope of the linear regions of each plot, representing acceleration towards a steady-state, were used to determine relative rates of activation for each AKT. Results: We developed a novel assay for AKT activation and substrate phosphorylation utilizing AQT0076, DOPS/DOPC, PIP3, PDK1, and MK2. With a mix of classical AKT inhibitors and allosteric inhibitors that rely on an inactive “PH-in” conformation, we demonstrated inhibition and quantified inhibitor potency of both active “PH-out” AKT activity and inactive “PH-in” AKT activation via dose-response measurements of steady-state rate and rate acceleration, respectively. Conclusions: A robust, homogeneous assay was developed to simultaneously monitor AKT activation and substrate phosphorylation kinetically over time. Through a continuous assay, we captured both steady-state rates and rate acceleration as a function of inhibitor concentration, allowing for accurate quantitation of both classes of AKT inhibitors in a single experimental format. With some inhibitors, we observed potencies that matched reported literature values, while with others we observed marked differences that may reflect a more physiological context that could translate through to higher efficacy in the clinic. This novel assay format provides a new tool that can be used in drug discovery to generate more effective next generation inhibitors of both AKT activation and subsequent substrate phosphorylation to prevent cancer cell growth and progression. Citation Format: Susan Cornell-Kennon, Daniel Urul, Matthew Hakar, Hayley McMahon, Khanh Huynh, Earl May, Erik Schaefer. A novel sox-based continuous and homogeneous assay for the discovery of inhibitors of inactive and active AKT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1666.

An Eco-friendly Mangifera indica Leaves Extract Corrosion Inhibitor for Stainless Steel in Acidic Medium

Corrosion of metals and alloys is one of the most frequent problems encountered in chemical and process industries. Inefficient corrosion control measures typically lead to an increased risk of unplanned downtime, huge economic loss, environmental damage, and health and safety hazards. Hence, it is essential to develop environment-friendly and cost-effective corrosion inhibitors over existing toxic anticorrosive agents. The main objective of this work is to examine the efficacy of eco-friendly ethanolic extract of Mangifera indica leaves (MIL) in different concentrations as a green corrosion inhibitor for stainless steel (SS-316L) under an acidic environment. The inhibition efficiency of Mangifera indica leaves extract in 1 M hydrochloric acid (HCl) was evaluated by conventional weight loss method along with adsorption isotherm analysis. Chemical compounds present in leaf extract and changes in surface morphology of SS-316L samples were assessed using Fourier Transform Infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FE-SEM) provided with elemental analysis. The results of the weight loss method revealed that the inhibition efficiency increases with increasing MIL extract concentration due to higher surface coverage. The highest inhibition efficiency of almost 63.43% in 14 days and minimum corrosion rate of 0.433 mm per year was obtained for SS-316 L in 1.0 M HCl with 1000 ppm concentration. The adsorption of MIL extract on SS-316L surface followed Freundlich adsorption isotherm, and the obtained value of free Energy of adsorption (ΔG˚ads = – 9.20 kJ.mol-1) indicates the physical adsorption mechanism. The developed regression-based models can predict the corrosion rate as a function of inhibitor concentration and exposure time with good accuracy (>80%). Thus, the present findings demonstrate that Mangifera indica L. leaves extract can suitably be applied as an inexpensive, non-toxic, biodegradable, efficient green corrosion inhibitor for the protection of stainless steel in acidic media.

Synthesis, spectroscopic analysis and electrochemical studies of novel organic compound based on N-alkylphthalazinone chemistry as corrosion inhibitor for carbon steel in 1M HCl

The adsorption affinity and corrosion protection of two synthesized N-alkylphthalazinone derivatives 2(a-b), namely: 2-(prop-2-yn-1-yl)-4-(p-tolyl)phthalazin-1(2H)-one (a) and 4-(4-chlorophenyl)-2-(prop-2-yn-1-yl)phthalazin-1(2H)-one (b) on carbon steel (CS) in an acidic environment using electrochemical and mass loss methods. The mass loss test at the highest inhibitor concentration produced a maximum corrosion efficiency of 93.4% for inhibitor (a). Thermodynamic parameters were determined while the inhibitors' adsorption process was investigated. The inhibitory molecules adsorption on the CS substrate accompanied the Langmuir isotherm. As a function of inhibitor concentration, the thermodynamic activation functions of the dissolution process were calculated. Surface examination such as scanning electron microscopy (SEM), fourier transfer infrared spectroscopy (FTIR), and atomic force microscopy (AFM) techniques were used to confirm the adsorption phenomenon. Also investigated were quantum chemical parameters to approve the donor-acceptor system of the synthesized N-alkylphthalazinone derivatives. The theoretical values are in good correlation with the experimental values.

Insights into the adsorption and corrosion inhibition properties of newly synthesized diazinyl derivatives for mild steel in hydrochloric acid: synthesis, electrochemical, SRB biological resistivity and quantum chemical calculations.

Two azo derivatives, 4-((4-hydroxy-3-((4-oxo-2-thioxothiazolidin-5-ylidene)methyl)phenyl) diazinyl) benzenesulfonic acid (TODB) and 4-((3-((4,4-dimethyl-2,6-dioxocyclohexylidene) methyl)-4-hydroxyphenyl)diazinyl) benzenesulfonic acid (DODB) were synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR) and mass spectral studies. Gravimetric methods, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM) techniques and inductive coupled plasma-optical emission spectroscopy were used to verify the above two compounds' ability to operate as mild steel (MS) corrosion inhibitors in 1 M HCl. Tafel data suggest that TODB and DODB have mixed-type characteristics, and EIS findings demonstrate that increasing their concentration not only alters the charge transfer (R ct) of mild steel from 6.88 Ω cm2 to 112.9 Ω cm2 but also changes the capacitance of the adsorbed double layer (C dl) from 225.36 to 348.36 μF cm-2. At 7.5 × 10-4 M concentration, the azo derivatives showed the highest corrosion inhibition of 94.9% and 93.6%. The inhibitory molecule adsorption on the metal substrate followed the Langmuir isotherm. The thermodynamic activation functions of the dissolution process were also calculated as a function of inhibitor concentration. UV-vis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) techniques were used to confirm the adsorption phenomenon. The quantum chemical parameters, inductively coupled plasma atomic emission spectroscopy (ICPE) measurements, and the anti-bacterial effect of these new derivatives against sulfate-reducing bacteria (SRB) were also investigated. Taken together, the acquired results demonstrate that these compounds can create an appropriate preventing surface and regulate the corrosion rate.

Modelling of the kinetics of red tilapia (Oreochromis spp.) viscera enzymatic hydrolysis using mathematical and neural network models

The present work modelled the enzymatic hydrolysis of red tilapia (Oreochromis spp.) viscera with Alcalase® 2.4 L in both 0.5 and 5 L reactors. The best conditions for the enzymatic hydrolysis were 60°C and pH 10. The product inhibited the enzymatic hydrolysis, and the enzyme deactivated following second-order reaction. K_M and K_p from a secondary plot of K_M^app as a function of inhibitor concentration, and k_2, p, and k_3 were found by non-linear regression. While the obtained parameters modelled the 0.5 L reactor well, it did not model the 5 L reactor, probably because of unconsidered fluid dynamics in the model. To have a better modelling, a neural network (tensorflow.keras.models module) was built and trained. The neural network modelled the enzymatic hydrolysis of red tilapia at several concentrations of substrate and enzyme. This result proved that neural networks are a powerful tool for modelling biological processes.

Corrosion inhibition of aluminium in hydrochloric acid medium using cimetidine as inhibitor: empirical and optimization studies

PurposeThe purpose of this study was to investigate cimetidine as corrosion inhibitor of aluminium in hydrochloric acid medium.Design/methodology/approachCimetidine was characterized by gas chromatography mass spectrophotometer and Fourier transform infrared spectroscopy to determine its chemical composition and functional groups, respectively. Gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopic techniques were used in the corrosion inhibition process. Thermodynamic and adsorption parameters were evaluated. And response surface methodology was used to optimize the corrosion inhibition process.FindingsAnalysis of the results revealed that major constituents of cimetidine include metronidazole, n-hexadecanoic acid cyclohexane and methyl ester. It has C-H stretch, C = N stretch, CH3C-H bend, ring C = C stretch, -C-O-O stretch, N-H bend, C-O stretch and C-H bend as predominant functional groups. Adsorption of molecules of the inhibitor on the aluminium surface was spontaneous, and it followed mechanism of physical adsorption. Response surface methodology revealed that quadratic model adequately described the inhibition efficiency of cimetidine as function of inhibitor concentration, temperature and time. Chemical and electrochemical results are in agreement that the cimetidine is a viable corrosion inhibitor. Cimetidine was revealed as mixed-type inhibitor because it controlled both cathodic and anodic reactions.Originality/valueEmpirical and optimization studies of cimetidine drug as corrosion inhibitor of aluminium in hydrochloric acid medium were carried out. The research results can provide the basis for deploying drugs (with mucosal protective and antacid properties) for corrosion control of metallic structures.

PHYTOCHEMICALS AND INHIBITIVE PROPERTIES OF CASHEW EXTRACT AS CORROSION INHIBITOR OF ALUMINIUM IN H2SO4 MEDIUM

This work studied the phytochemicals and inhibitive properties of cashew extract as corrosion inhibitor of aluminium in H2SO4 medium. Qualitative and quantitative analyses of the cashew extract were carried out to identify and quantify the phytochemicals for the corrosion inhibition process. Thermometric and gravimetric techniques were employed in the study of corrosion inhibition of aluminium in H2SO4 medium. The inhibition efficiency of the cashew extract was modeled using Response Surface Methodology (RSM) of Design Expert Software 9. It was revealed that phytochemicals of alkaloids, cardiac glycosides, flavonoids, phenolics, phytates, saponins and tanins were present in the cashew extract at various degrees. The cashew extract is predominantly made of flavonoids (425.0mg/100g) followed by alkaloids (221.7mg/100g).Adsorption of the cashew extract on the Al surface obeyed physical adsorption mechanism. Thermometric and gravimetric techniques are in agreement of recording high inhibition efficiencies of 83.7% and 82.5% respectively. The phytochemicals of the cashew extract are good inhibitive agents for the corrosion control process. A quadratic model is adequate for the description of the inhibition efficiency of the cashew extract as a function of inhibitor concentration, temperature and time.

Data Mining Model for Prediction Effect of Corrosion Inhibition

Electrochemical impedance Nyquist tests have become a common technique to study corrosion inhibition behavior of steel. Methionine has been investigated as corrosion inhibitor for carbon steel (C-steel) in 1 M HCl solution using electrochemical impedance spectroscopy (EIS). Based on these experimental tests, the efficiency of the inhibitor increases with increase in the inhibitor concentration and decreases with increase in temperature. In this paper, a model based on neural networks is presented in order to obtain predictions of imaginary impedance based on the real part of the impedance as a function of inhibitor concentration and temperature. For the network, the learning algorithm, the hyperbolic tangent sigmoid transfer function, and the linear transfer function were used. The results based on correlation coefficient and root-mean-square show the utility of this tool to predict impedance values without requiring the use of EIS tests.

Evaluation of the corrosion inhibition potentials of green-tip forest lily (<i>Clivia nobilis</i>) <i>leaves extract</i> on mild steel in acid media

Plant extracts are excellent alternatives as corrosion inhibitors because of availability, low toxicity, biodegradability and low cost. In this study, corrosion tests were performed on mild steel to evaluate the effect of concentration of inhibitor, varying immersion period and temperature on the corrosion inhibition properties of Clivia nobilis leaves extract. This was done in H2SO4 and HCl acid solutions using weight loss and gasometric methods. From the weight loss results, corrosion rate and degree of surface coverage were evaluated and plotted as a function of inhibitor concentration at various immersion times. The volume of the cathodic hydrogen gas evolved was also plotted as a function of inhibitor concentration. The efficiency of inhibition in H2SO4 and HCl solutions were also compared. It was observed that corrosion inhibition efficiency increased with increasing concentration of Clivia nobilis leaf extract but not with prolonged immersion period. Experimental data obtained at 313 and 333K fitted the Freundlich and Langmuir isotherms, suggesting adsorption of Clivia nobilis leaves extract on the metal surface. Activation energy data described the interaction as electrostatic.Keywords: Extract, corrosion, inhibitor, concentration, leaves

Biochemical Characterization of GS-4059 As a Potent and Selective Covalent Irreversible Inhibitor of Bruton's Tyrosine Kinase

Introduction:Bruton's tyrosine kinase (BTK) plays a crucial role in B-cell development, differentiation, and signaling in the B-cell receptor (BCR) signaling pathway, and is a validated target for aberrant B-cell activity in malignancy and autoimmune diseases. GS-4059 (ONO-4059) is a selective, once-daily, oral inhibitor of BTK with clinical activity against a number of relapsed/refractory B-cell malignancies. GS-4059 was designed to specifically form a covalent bond with a cysteine residue in the BTK active site. The studies presented here confirmed the biochemical mechanism of action of GS-4059, assessed the inactivation kinetics of BTK by GS-4059 and comparator compounds, and measured the selectivity of GS-4059 for BTK over other related kinases. These studies will help to establish pharmacokinetic-pharmacodynamic models to guide clinical studies, and the evaluation of potential for inhibition of other kinases will assist in understanding the safety of the molecule.Methods: The binding of GS-4059 to BTK was characterized using mass spectrometry to detect covalent adduct formation. Ibrutinib, a known irreversible covalent inhibitor, and staurosporine, a known reversible noncovalent inhibitor, were used as positive controls. The covalent nature of GS-4059 was further tested by chasing with excess amount of ibrutinib. GS-4059 and other covalent, irreversible inhibitors of BTK including CC-292, acalabrutinib, and ibrutinib were studied to determine the inactivation kinetics of BTK and related kinases, such as epidermal growth factor receptor (EGFR) and IL2-inducible T-cell kinase (ITK), for these compounds. The rate of enzyme inactivation was studied as a function of inhibitor concentration using a Sox-based fluorescence assay that allows real-time measurement of enzyme activity.Results: Mass spectrometry studies showed that GS-4059 is a covalent inhibitor of BTK, based on an observed mass shift of BTK following preincubation with GS-4059 (Figure 1). This mass shift was consistent with the molecular weight of GS-4059. The irreversibility of GS-4059 binding was further demonstrated by the observation that GS-4059 could not be displaced from BTK by chasing with ibrutinib, as measured by mass spectrometry. GS-4059 efficiently inactivated BTK with a rate constant kinact/Ki of 2.4 ± 0.6 ´ 104 M-1s-1, similar to that of the covalent BTK inhibitors CC-292 and acalabrutinib, but >10 times lower than that of ibrutinib (Figure 2, Figure 3, and Table 1). In addition, GS-4059 is a poor inhibitor of the related kinases EGFR and ITK, supporting the clinical observation of a favorable safety profile for GS-4059 (Table 1).Conclusions: In summary, GS-4059 is a potent and selective covalent irreversible inhibitor of BTK with a different selectivity profile than other BTK inhibitors, and warrants further studies against B-cell malignancies and autoimmune diseases. [Display omitted] [Display omitted] [Display omitted] DisclosuresLiclican:Gilead Sciences: Employment, Equity Ownership. Xing:Gilead Sciences: Employment, Equity Ownership. Serafini:Gilead Sciences: Employment, Equity Ownership. Wang:Gilead Sciences: Employment, Equity Ownership. Brendza:Gilead Sciences: Employment, Equity Ownership. Lutz:Gilead Sciences: Employment, Equity Ownership. Ray:Gilead Sciences: Employment, Equity Ownership. Schultz:Gilead Sciences: Employment, Equity Ownership. Sakowicz:Gilead Sciences: Employment, Equity Ownership. Feng:Gilead Sciences: Employment, Equity Ownership.

Retardation of High-Temperature Fuel Ash Corrosion of Fireside Boiler Tubes via Nanoparticles

The high-temperature corrosion rate of boiler tubes was studied as a function of inhibitor concentration, time, and temperature in the absence and presence of fuel ash. Samples of steel tubes were taken from boilers that operate in Northern Baghdad Station for Electric Power Generation. Fuel ash was collected from the boiler combustion chamber, as well. Normal and nano-MgO were used as a corrosion inhibitor in different mixing ratios. A weight loss technique was used to evaluate the corrosion rates, while scanning electron microscopy was used to study the surface morphology. It was seen that corrosion rates increased with both time and temperature, and decreased with the addition of inhibitors. The maximum inhibitor efficiency was 81 %, obtained via using nano-MgO at mixing weight ratio 2:1, 600 °C, and 10 h. The Presence of fuel ash had harmful effects on the steel surface.

Electrochemical Evaluation of an Outdated Antifungal Drug as Corrosion Inhibitor of Mild Steel in Neutral Chloride Media

The anti-corrosion behavior of expired Fluconazole (2-(2,4-Difluorophenyl)-1,3-di(1H-1,2,4- triazol-1-yl)-2-propanol) as an inhibitor on mild steel was studied in a neutral chloride/sulphate solution, at room temperature using electrochemical techniques including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Fluconazole characterization was performed using FTIR. Polarization curves showed that both corrosion and film formed pseudo-passivation current density values were lowered by almost one order of magnitude and therefore fluconazole acts as an anodic type of inhibitor on the steel surface. Impedance measurements confirmed the decrease in the corrosion rate by almost an order of magnitude, as a function of inhibitor concentration. The electrochemical results showed that this compound has a corrosion inhibitor effect and the best results were achieved with 150 ppm of Fluconazole, remaining around 80% efficiency up to 160 hours of immersion. Keywords: Electrochemistry, fluconazole (2-(2, 4-Difluorophenyl)-1, 3-di(1H-1, 2, 4-triazol-1-yl)-2-propanol), inhibitor, neutral chloride, steel corrosion.

Inhibition of AA2024-T351 Corrosion Using Permanganate

The inhibition of corrosion on AA2024-T351 in NaCl solutions, mitigated by either in-situ permanganate ions (MnO4−) or permanganate pretreatment, was examined. Both room temperature pretreatment and solution phase additions were studied as a function of inhibitor concentration. The roles of the inhibitor during anodic and cathodic polarizations were investigated. Inhibition of corrosion at open circuit corrosion potential (OCP) under conditions where anodic and cathodic reactions are coupled was also examined. The oxidation states of the manganese oxides that contributed to protection were determined using potentiometric electrochemical reduction and in-situ Raman spectroscopy. The thermodynamics of the Mn-water system was also considered over a range of concentrations. Permanganate was shown to be both an anodic and cathodic inhibitor, and an inhibitor of copper replating at OCP.

A New Approach for Predicting Inhibited Erosion-Corrosion in CO2-Saturated Oil/Brine Flow Condition

Summary Chemical inhibition is a common method for controlling erosion-corrosion in offshore mild steel pipelines, tubing and pipe fittings. This paper introduces a new approach for predicting inhibited erosion-corrosion in mild steel pipes, including the effects of flow and environmental conditions, sand production, and an oil phase. When sand is produced, sand particle impingement on piping surfaces can decrease the efficiency of corrosion protection systems, such as iron-carbonate scale formation or chemical inhibition, and can result in severe corrosion and even pitting. The need to be able to predict inhibitor performance under sand-production conditions is particularly acute when the wells are deep or offshore because of the difficulty in running coupon tests to evaluate the inhibitor efficiency at critical points throughout a system. The research reported in this paper is aimed at providing producers with information that will help them make decisions on the design of the well given advanced knowledge of the inhibition options and their predicted effectiveness under sand-production conditions. Inhibition mechanisms and the relation between inhibitor concentration and inhibitor coverage are described using adsorption isotherms. The Frumkin isotherm showed the best fit to experimental data for an imidazoline-based inhibitor used in sand-free conditions. Flow-loop tests indicated that sand particle erosion decreased the efficiency of the inhibitor. However, Frumkin isotherms modified to handle effects of erosivity, temperature, and oil phase were successfully fitted to erosion-corrosion data. Inhibitor adsorption isotherms, for both sand-free and sand-production conditions, were integrated into a mechanistic model for prediction of CO2 corrosion rates as a function of inhibitor concentration, and good results were obtained when compared with data. Results of this study show that the inhibitor adsorption isotherm, modified to handle effects of sand production, temperature, and oil phase, can be a valuable tool for predicting inhibited metal loss rates under sand-production conditions.

Characterization and Prediction of Chemical Inhibition Performance for Erosion-Corrosion Conditions in Sweet Oil and Gas Production

The effects of sand erosion on inhibitor performance have been examined in a flow loop using an impinging jet test cell and different techniques such as long-term weight loss (WL), linear polarization resistance (LPR), potentiodynamic polarization (PDYN), 3-D profilometry, and electrochemical impedance spectroscopy (EIS). Inhibition mechanisms and the relation between inhibitor concentration and corrosion penetration rate are described by the Flory-Huggins, Frumkin, Temkin, and Langmuir adsorption isotherms. Flow loop tests indicated that sand particle erosion can decrease the efficiency of an imidazoline-based inhibitor by removing the inhibitor protective layer from the surface. Therefore, an increased concentration of inhibitor is needed during sand production to achieve the same effectiveness. It was shown that an inhibitor adsorption isotherm can be integrated into a mechanistic model for prediction of carbon dioxide (CO2) corrosion to predict CO2 corrosion rates as a function of inhibitor concentration. Also, the inhibitor adsorption isotherm has been modified as a function of erosivity to predict the effect of erosivity on corrosion inhibition. One novel approach is discussed for predicting the inhibited erosion-corrosion rate based on the modified inhibitor adsorption isotherms combined with mechanistic models for predicting CO2 corrosion rates and sand particle erosion rates.

Adsorption and inhibition effect of benzotriazole on brass-118 and brass-MM55 in artificial seawater

Corrosion behaviours of the new type special commercial brass alloys, called 118 and MM55, have been investigated by Tafel Extrapolation (TP) and Linear Polarization (LP) methods in artificial seawater. Inhibition effect of benzotrizole (BTA) of four different concentrations for the corrosion of brass samples was investigated. It was found that BTA was acting as mixed type inhibitor and inhibition efficiency was increasing with the increase of BTA concentration. The change of the degree of surface coverage (θ) as a function of inhibitor concentration (c) shows that BTA follows Langmuir adsorption isotherm. Values of adsorption equilibrium constants (K ads) and values of free energies of adsorption (ΔG ads) were calculated from adsorption isotherms. Results reveal that chemisorption is the initial step of inhibition processes.

Crystal Structure of Mycobacterium tuberculosis Zinc-dependent Metalloprotease-1 (Zmp1), a Metalloprotease Involved in Pathogenicity

Mycobacterium tuberculosis, the causative agent of tuberculosis, parasitizes host macrophages. The resistance of the tubercle bacilli to the macrophage hostile environment relates to their ability to impair phagosome maturation and its fusion with the lysosome, thus preventing the formation of the phago-lysosome and eventually arresting the process of phagocytosis. The M. tuberculosis zinc-dependent metalloprotease Zmp1 has been proposed to play a key role in the process of phagosome maturation inhibition and emerged as an important player in pathogenesis. Here, we report the crystal structure of wild-type Zmp1 at 2.6 Å resolution in complex with the generic zinc metalloprotease inhibitor phosphoramidon, which we demonstrated to inhibit the enzyme potently. Our data represent the first structural characterization of a bacterial member of the zinc-dependent M13 endopeptidase family and revealed a significant degree of conservation with eukaryotic enzymes. However, structural comparison of the Zmp1-phosphoramidon complex with homologous human proteins neprilysin and endothelin-converting enzyme-1 revealed unique features of the Zmp1 active site to be exploited for the rational design of specific inhibitors that may prove useful as a pharmacological tool for better understanding Zmp1 biological function.

Monitoring corrosion and corrosion control of iron in HCl by non-ionic surfactants of the TRITON-X series – Part III. Immersion time effects and theoretical studies

The inhibition performance of three selected non-ionic surfactants of the TRITON-X series, namely TRITONX-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on the corrosion of iron was studied in 1.0 M HCl solutions as a function of inhibitor concentration (0.01–0.20 g L −1) and immersion time (0.0–8 h) at 298 K. Measurements were conducted based on Tafel polarization, LPR and impedance studies. At high frequencies, the impedance spectrum showed a depressed capacitive loop in the complex impedance plane, whose diameter is a function of the immersion time and the type and concentration of the introduced surfactant. In all cases, an inductive loop was observed in the low frequency and this could be attributed to the adsorption behavior. The inhibition efficiency increased with immersion time, reached a maximum and then decreased. This was attributed to the orientation change of adsorbed surfactant molecules. TX-305 inhibited iron corrosion more effectively than TX-100 and TX-165. The frontier orbital energies, the energy gap between frontier orbitals, dipole moments ( μ), charges on the C and O atoms, the polarizabilities, and the quantum chemical descriptors were calculated. The quantum chemical calculation results inferred that for the HOMO representing the condensed Fukui function for an electrophilic attack ( f k + ), the contributions belong to the phenyl group and the oxygen atom attached to the phenyl group for each tested surfactant. Quantitative structure–activity relationship (QSAR) approach has also been used and a correlation of the composite index having some of the quantum chemical parameters with average inhibition efficiencies ( I av.(%)) was conducted to determine the inhibition performance of the tested surfactant molecules. The results showed that the values of I av.(%) of the tested inhibitor molecules were closely related to some of the quantum chemical parameters. The calculated I av.(%) values were found to be close to the experimental ones. Based on the values of coefficients of correlations at 0.02 level concentration, B3LYP/3-21G ∗ method outpaced the other two methods namely B3LYP/6-31G and RHF/6-31G ∗. The relationship between I av.(%) and composite index is accounted for by B3LYP/3–21G ∗.

Monitoring corrosion and corrosion control of iron in HCl by non-ionic surfactants of the TRITON-X series – Part II. Temperature effect, activation energies and thermodynamics of adsorption

The inhibition characteristics of non-ionic surfactants of the TRITON-X series, namely TRITON-X-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on the corrosion of iron was studied in 1.0 M HCl solutions as a function of inhibitor concentration (0.005–0.075 g L −1) and solution temperature (278–338 K). Measurements were conducted based on Tafel extrapolation method. Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented. Experimental corrosion rates determined by the Tafel extrapolation method were compared with corrosion rates obtained by the EFM technique and an independent method of chemical analysis. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry). The aim was to confirm validation of corrosion rates measured by the Tafel extrapolation method. Results obtained showed that, in all cases, the inhibition efficiency increased with increase in temperature, suggesting that chemical adsorption occurs. The adsorptive behaviour of the three surfactants followed Temkin-type isotherm. The standard free energies of adsorption decreased with temperature, reflecting better inhibition performance. These findings confirm chemisorption of the tested inhibitors. Thermodynamic activation functions of the dissolution process were also calculated as a function of each inhibitor concentration. All the results obtained from the methods employed are in reasonable agreement.