Variation Of Inhibition Efficiency Research Articles

Locust Bean Gum as Corrosion Inhibitors in NaCl Solution

In this research, the inhibitive performance of locust bean gum (LBG) on the corrosion behavior of AISI 304 stainless steel (AISI 304SS), E150 Al alloy and copper in 0.15 M NaCl containing various amounts (10–3, 10–2, 10–1, 1, 1.5 and 2 g L–1) of LBG were researched using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X‑ray analysis (EDS) and inductively coupled plasma optical emmision spectrometry (ICP-OES) methods. Polarisation curves indicated that LBG was acting as mixed type inhibitor. All electrochemical measurements showed that inhibition efficiencies increased with increasing LBG concentration. It was determined that the increase of inhibitor efficiency by concentration resulted from the adsorption of LBG to metal surface, and the adsorption fitted to the Langmuir adsorption isotherm equation. The variation in inhibitive efficiency mainly depends on sugar units present in the LBG molecule. The best inhibition shows in 0.15 M NaCl + 2 g L–1 LBG solution. LBG reduced corrosion by slowing the rate of reactions formation without changing anodic and cathodic reactions. In addition, LBG adsorptioned on active sites caused the reduction of corrosion due to geometric block effect. SEM results show that metal surfaces are highly damaged in an inhibitor-free environment. The SEM images with inhibitor environment show that the surface is more homogeneous and smooth. The results of EDS show that the presence of oxygen in the inhibitor medium results in the formation of surface metal oxides, and therefore the reduction of corrosion.

Corrosion inhibition and adsorption properties of cerium-amino acid complexes on mild steel in acidic media: Experimental and DFT studies

The corrosion inhibition and adsorption behavior of glutamic acid (Glu), glutamine (Gln), and their cerium complexes: cerium glutamate (Ce(Glu)) and cerium glutamine (Ce(Gln)) on mild steel in 0.5 M HCl solutions were studied at 25 and 55 °C and concentration range of 25–200 ppm using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopic (EIS) techniques. The inhibition efficiency was found to be dependent on the concentration and temperature of the system. The potentiodynamic polarization results suggest that the compounds act as mixed-type inhibitors with dominant cathodic inhibition. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature, as well as the activation parameters, suggest significant physisorption of the inhibitor molecules on the metal surface. The experimental data adhere to the Langmuir and El-Awady et al. kinetic adsorption models. The extent of inhibition was found to be Ce-Gln > Gln and Ce-Glu > Glu. The scanning electron microscope was employed for the morphological studies and the characteristic of the protective layer on the steel surface verified using UV-Vis spectroscopy and FTIR spectroscopy. Adsorption of the inhibitors on Fe (110) surface was evaluated theoretically.

Tertiary Amine Methacrylate based Polymers as Corrosion Inhibitors in HCl Solution. Part II

In this study, the inhibitive performance of novel synthesised water-soluble of different molecular weight diblock copolymers of derivative methyl methacrylate (VB84, VB206, VB207, VB361, VB371,VB406) on the corrosion behavior of AISI 304 stainless steel in 10–3 M HCl containing various concentrations of polymers was investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), scanning electron microscopy(SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and inductively coupled plasma optical emmision spectrometry (ICP-OES) methods. Polarisation curves indicated that all studied polymers were acting as mixed type inhibitors. All electrochemical measurements showed that inhibition efficiencies increased with increasing polymer concentration. It was determined that the increase of inhibitor efficiency by concentration resulted from the adsorption of polymers to metal surface, and the adsorption fitted to the Langmuir adsorption equation. The variation in inhibitive efficiency mainly depends on the type and the nature of the substituents present in the polymer molecule and also depends on the molecular weight of the polymer. The best inhibition in 10-3 M HCl shows VB84 homopolymer. Surface images obtained with SEM, EDX, and AFM methods determined by verifying these results that inhibitors decrease the dissolution of metal, prevented the corrosion.

Tertiary Amine Methacrylate based Polymers as Corrosion Inhibitors in Double Distilled Water. Part I

In the current study, the inhibitive performances of tertiary amine methacrylate based water soluble diblock copolymers on the corrosion behavior of AISI 304 stainless steel were investigated in double distilled water (DDW, at pH 7.6) using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and inductively coupled plasma optical emmision spectrometry (ICP OES) methods. Related diblock copolymers were poly[2-(dimethylamino)ethylmethacrylate] (PDMA), poly[2-(diethylamino)ethylmethacrylate] (PDEA), poly[2-(diisopropylamino)ethylmethacrylate] (PDPA) homopolymers and poly[2-(dimethylamino)ethylmethacrylate]-b-poly[methylmethacrylate] (PDMA-b-PMMA), poly[2-(diethylamino)ethylmethacrylate]-b-poly[methylmethacrylate] (PDEA-b-PDMA) and poly[2-(diisopropylamino)ethylmethacrylate]-b-poly[2-(dimethylamino)ethylmethacrylate] (PDPA-b-PDMA). Diblock copolymers having different molecular weight and different comonomer ratios. Polarisation curves indicated that all the studied polymers were acting as a mixed type inhibitors. All electrochemical measurements showed that inhibition efficiencies increased with an increase in the inhibitor concentration. It was determined that the increase of inhibitor efficiency by concentration resulted from the adsorption of polymers to metal surface, and the adsorption fitted to Langmuir adsorption equation. Adsorption equilibrium constant (Kads) and free energy of adsorption(ΔGads), which were thermodynamic parameters of adsorption were calculated by benefiting from the drawn adsorption isotherms. The variation in inhibitive efficiency mainly depended on the type and the nature of the substituents present in the inhibitor molecule and also depended on the molecular weight of the inhibitors. The best inhibition in DDW showed VB207 diblock copolymer. Surface images obtained with SEM, EDX and AFM methods, determined by verifying these results that inhibitors decreased the dissolution of metal, and prevented the corrosion.

Experimental and Theoretical Evaluation of Rutin as Eco-Friendly Corrosion Inhibitor for Aluminum 6063 Alloy in Acidic Medium

The corrosion inhibition characteristics of rutin a natural flavonoid glycoside has been studied as an eco-friendly green inhibitor for corrosion control of aluminum alloy AA6063 in 0.5 M HCl medium at a temperature range of 30–60 °C by weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The inhibition efficiency increased with the increase in concentration of the inhibitor and also with increase in temperature. The surface morphologies of the polished, corroded and inhibited surfaces were scanned using the scanning electron microscope images. The activation parameters like energy of activation, enthalpy of activation and entropy of activation were calculated and analyzed. Thermodynamic parameters for the adsorption of the inhibitor on the metal alloy surface were calculated and analyzed. The inhibitor acted as a mixed inhibitor. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature as well as kinetic and activation parameters suggests significant chemisorption of the inhibitor on the metal surface. The mechanism of inhibition can partly be attributed to the possible coordination of rutin to form stable aluminum–rutin complex. The maximum inhibition efficiency was found to be 95.1 and 94.45% by PDP and EIS studies, respectively, at 60 °C. Density functional theory calculations under the level B3LYP/6-311G(d) is utilized for the calculation of quantum chemical parameters.

Corrosion Inhibition Potential of Ethanol Extract of Bryophyllum pinnatum Leaves for Zinc in Acidic Medium

The inhibitive and adsorption properties of ethanol extract of Bryophyllum pinnatum leaves were studied using weight loss, potentiodynamic polarization, Scanning Electron Microscopy (SEM) and Fourier transformed infra-red spectroscopy (FTIR) methods of monitoring corrosion. The results obtained, indicated that ethanol extracts of Bryophyllum pinnatum leaves is a good adsorption inhibitor for the corrosion of zinc in sulphuric acid solutions. The adsorption of the inhibitor on zinc surface was found to be spontaneous and supported the Langmuir adsorption model. From the calculated values of free energy of adsorption, the activation energy and the variation of inhibition efficiency with temperature, a physical adsorption mechanism has been proposed for the adsorption of ethanol extract of Bryophyllum pinnatum leaves on zinc surface. Results from potentiodynamic polarization study indicated that Bryophyllum pinnatum is a mixed-type corrosion inhibitor. Analysis of spectra obtained from Fourier transformed infra-red spectrophotometer (FTIR) revealed that some functional groups presence in the spectra of the inhibitors were missing in the spectra of the corrosion products which also indicated that there is an interaction between zinc and the inhibitor.

Synergistic inhibition of aluminium corrosion in H2SO4 solution by polypropylene glycol in the presence of iodide ions

Purpose The purpose of this paper is to evaluate the performance of polypropylene glycol (PPG), as a corrosion inhibitor for aluminium corrosion in 0.5 M H2SO4 solution at 303-333 K and the effect of addition of iodide ions on the corrosion inhibition efficacy of PPG. Design/methodology/approach The corrosion inhibition performance of PPG alone and on addition of iodide ions in the acid medium was evaluated using weight loss and electrochemical [electrochemical impedance spectroscopy (EIS), linear polarisation resistance (LPR) and potentiodynamic polarization (PDP)] methods as well as surface analysis approach at 303-333 K. The morphology of the corroding aluminium surface without and with the additives was visualised using scanning electron microscopy (SEM). The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption. Findings Results obtained showed that PPG moderately retarded the corrosion of Al in 0.5 M H2SO4 solution. Addition of KI to PPG is found to synergistically improve the inhibitive ability of PPG. From the variation of inhibition efficiency, K_ads, and E_a, with rise in temperature, physisorption mechanism is proposed for the adsorption of PPG and PPG + KI onto the Al surface in 0.5 M H2SO4 solution. Polarisation results showed that PPG and PPG + KI acted as mixed type inhibitor. The adsorption of PPG and PPG + KI, respectively, onto the metal surface followed El-Awady et al. adsorption isotherm model. SEM and water contact angle analysis confirmed the adsorption of PPG and PPG + KI on Al surface. Research limitations/implications The research is limited to aqueous acid environment in aerated condition, and all tests were performed under static conditions. Practical implications The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal. Originality/value The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal.

English

The inhibition of mild steel corrosion in 0.5 M sulphuric acid solution by ethanol extracts of Parinari polyandra as an eco-friendly inhibitor was studied at different temperatures by weight loss technique and linear polarization. The test plant extracts has a promising inhibitory action against corrosion of mild steel in the sulphuric acid media. The inhibition efficiencies increase with a corresponding increase in the concentration of the inhibitor. The adsorption of the inhibitor on mild steel surface is exothermic, spontaneous and is best described by Freundlich and Temkim adsorption models. Calculated values of activation energy, enthalpy of activation, entropy of activation, free energy of adsorption and the trend in the variation of inhibition efficiency with temperature, the mechanism of the process is by physical adsorption. Ethanol extract of Parinari polyandra is a good adsorption inhibitor for the corrosion of mild steel in sulphuric acid. Tafel polarization analyses indicate that the studied plant extract is a mixed type inhibitor. Key words: Isotherm, polarization, adsorption, inhibitor, Parinari polyandra.

Comparative Study of the Corrosion Inhibition Efficacy of Polypropylene Glycol and Poly (Methacrylic Acid) for Mild Steel in Acid Solution

The performance of polypropylene glycol (PPG) and poly (methacrylic acid) (PMAA) as corrosion inhibitors for mild steel in acid solution was assessed by weight loss, electrochemical (electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization), and surface analysis (water contact angles) techniques. Results obtained showed that both polymers inhibited mild steel corrosion but PPG was the best inhibitor. Inhibition efficiency increased with the increase in inhibitor concentration but decreased with temperature rise. Polarization results show that both PPG and PMAA behaved as a mixed-type inhibitors. The adsorption of the polymers onto the mild steel surface followed Temkin adsorption isotherm model. The variation of inhibition efficiency with temperature point toward physical adsorption which is supported by the kinetic and thermodynamic parameters derived from the experimental data. Water contact angle measurement results show that the polymers were adsorbed onto the mild steel surface.

Influence of some synthesized pyrimidine derivatives on corrosion inhibition of mild steel in hydrochloric acid medium

The influence of four newly synthesized pyrimidine derivatives on the corrosion inhibition of mild steel in 0.5 M HCl solution is studied using mass loss and electrochemical techniques. The corrosion rate was found to depend on concentration and temperature of the medium. Adsorption of all the four inhibitors obeys Langmuir isotherm model. Polarization curves indicated that the studied inhibitors are of mixed type. Electrochemical impedance spectroscopy explains the mechanism of inhibitor’s action. Various activation and adsorption thermodynamic parameters were calculated and discussed. The results obtained from weight loss and electrochemical studies are in good agreement with each other. The variation in inhibitive efficiency mainly depends on the type and nature of the substituents present in the inhibitor molecule.

English

  The inhibiting effect of some chalcones derivatives on the corrosion of carbon steel in 1 M HCl was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The results showed that the inhibition efficiency increases with increasing the inhibitor concentration, while it decreases with increasing the temperature. The adsorption of chalcones derivatives on the carbon steel surface obeys Langmuir adsorption isotherm. Some thermodynamic parameters were calculated and discussed. The values of free energy of adsorption for investigated inhibitors were calculated. Polarization curves showed that chalcones derivatives are mixed-type inhibitors but the cathode is more polarized than the anode. The variation in inhibition efficiency depends on the type of the substituent groups in the benzene ring. It was found that the presence of donating group (such as OCH3) better facilitates the adsorption of molecules on the surface than in the case with withdrawing groups (such as – Cl and NO2). The data obtained from the four different methods were in good agreement.   Key words: Carbon steel, HCl, corrosion inhibition, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), chalcones derivatives.

Natural Products for Materials Protection: Mechanism of Corrosion Inhibition of Mild Steel by Acid Extracts of Piper guineense

The adsorption and corrosion inhibiting effect of acid extracts of Piper guineense (PG) leaves on mild steel corrosion in 1 M HCl and 0.5 M H2SO4 was investigated using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy techniques as well as scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The polarization and impedance results revealed that PG inhibited the cathodic and anodic partial reactions of the corrosion process via adsorption of the extract organic matter on the metal/solution interface. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature as well as kinetic and activation parameters suggest significant chemisorption of the extract constituents on the metal surface. Density functional theory calculations were performed to model the electronic structures of some extract constituents, including chemisorptive interactions with the Fe surface.

Inhibitive and adsorption properties of ethanol extract of Hibiscus sabdariffa calyx for the corrosion of mild steel in 0.1 M HCl

The inhibitive and adsorption properties of ethanol extract of Hibiscus sabdariffa calyx were studied using gravimetric, gasometric, thermometric, and Fourier transform infrared methods of monitoring corrosion. The results obtained indicated that ethanol extract of Hibiscus sabdariffa calyx is a good adsorption inhibitor for the corrosion of mild steel in HCl solutions. The adsorption of the inhibitor on mild steel surface is spontaneous and supports the Langmuir adsorption model. From the calculated values of free energy of adsorption, the activation energy, and the variation of inhibition efficiency with temperature, it can be concluded that the initial mechanism for the adsorption of ethanol extract of Hibiscus sabdariffa calyx on mild steel surface is physical adsorption. Analysis of spectra obtained from the Fourier transform infrared spectrophotometer indicated that there is an interaction between iron in mild steel and the inhibitor.

Joint Effect of Anogessius Leocarpus Gum (AL Gum) Exudate and Halide Ions on the Corrosion of Mild Steel in 0.1 M HCl

In an attempt to improve the corrosion inhibition potential of Anogessius leocarpus gum exudates for mild steel in solutions of HCl, corrosion inhibition efficiencies of the gum, KI, KCl, and KBr were determined experimentally using weight loss and gasometric methods. 0.05 M KI, 0.05 M KBr and 0.05 M KCl were combined with various concentrations of Anogessius leocarpus gum and their combined inhibition efficiencies were used in computing synergistic parameters for the respective combinations. The results obtained indicated that combination of 0.4 and 0.5 g/L of AL gum with 0.05 M solutions of KI and KBr, respectively, enhanced inhibition efficiency of the gum. However, for all concentrations of AL gum, combinations with 0.05 M KCl recorded a remarkable increase in inhibition efficiency, but calculated values of the synergistic parameter indicated that the adsorption of AL gum on mild steel surface is antagonized by the presence of Cl - . Theory of competitive and co-operative adsorption has been used to explain the co-adsorption of the gum and the halides. From calculated values of activation energy (< 80kJ/mol), free energy of adsorption (< -40 kJ/mol) and the variation of inhibition efficiency with temperature, the adsorption characteristics of the gum, halides and that of gum-halide mixtures were found to be consistent with the mechanism of physical adsorption. The adsorption was also found to be endothermic, spontaneous and favored the Langmuir adsorption model.

Isoindoline derivatives as inhibitors for the corrosion of carbon steel in HCl solution

The corrosion inhibition of carbon steel in 2.0 M HCl solution by four isoindoline derivatives has been investigated using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Tafel polarization showed that these derivatives are mixed-type inhibitors. The inhibition efficiency was found to increase with increasing concentration of inhibitor and decreases with increasing temperature. The Logarithmic isotherm was found to provide an accurate description of adsorption behavior of the isoindoline derivatives. Some thermodynamic parameters were computed and discussed. Synergistic study revealed that, the investigated anions (I−, Br− and SCN−) may enhance adsorption of the inhibitors. The variation in inhibition efficiency depends on the type of functional group substituted in benzene ring. It was found that the presence of donating group (such as CH3) better facilitates the adsorption of molecules on the surface than in the case with withdrawing groups (such as −H, −Br, and NO2). The data obtained from the three different methods are in good agreement.

Inhibition of the Corrosion of Zinc in 0.01 - 0.04 M H2SO4 by Erythromycin

Inhibition of the corrosion of zinc in 0.01 to 0.0 4 M H2SO4 by erythromycin was studied using weight loss and hydrogen evolution methods. The results obtained indicate that erythromycin is a good adsorption inhibitor for the corrosion of zinc in H2SO4 solutions. The inhibition efficiency of erythromycin increases with increasing concentration but decreases with increase in temperature. Thermodynamic and adsorption studies reveal that the adsorption of erythromycin on zinc surface is exothermic, spontaneous and is characterised with increasing degree of orderliness. The adsorption characteristics of the inhibitor are best described by the Langmuir adsorption model. From the variation of inhibition efficiency with temperature and the calculated values of the activation and free energies (which are within the limits expected for physical adsorption), we propose that the adsorption of erythromycin on zinc surface is consistent with the mechanism of physical adsorption.

Ethanol extract of Terminalia catappa as a green inhibitor for the corrosion of mild steel in H2SO4

The inhibitive and adsorption properties of ethanol extract of Terminalia catappa for the corrosion of mild steel in H2SO4 were investigated using weight loss, hydrogen evolution, and infra red methods of monitoring corrosion. Ethanol extract of T. catappa is a good adsorption inhibitor for the corrosion of mild steel in H2SO4. The inhibition efficiency of the inhibitor increases with increasing concentration but decreases with increasing temperature. The inhibition potential of ethanol extract of T. catappa is attributed to the presence of saponnin, tannin, phlobatin, anthraquinone, cardiac glycosides, flavanoid, terpene, and alkaloid in the extract. The adsorption of the inhibitor on mild steel surface is exothermic, spontaneous and is best described by Langmuir adsorption model. From the calculated values of activation energy, free energy of adsorption and the trend in the variation of inhibition efficiency with temperature, the mechanism of adsorption of the inhibitor is physical adsorption.

Protection of mild steel corrosion with new thia-derivative Salens in 0.5 M H2SO4 solution

The corrosion inhibition of mild steel in 0.5 M sulfuric acid by two newly synthesized Schiff bases namely, 4-X-2-{[2-(2-pyridin-2-yl-ethylsulfanyl) ethylimino] methyl}-phenol [X = –NO2 (S1) and –OMe (S2)] has been investigated in the temperature range 298–318 K using Tafel polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency of both S1 and S2 increases with increase in inhibitor concentration. The variation in inhibition efficiency depends on the type of functional group substituted in the benzene ring. It was found that the presence of the methoxy group in the Schiff base (S2) better facilitates the adsorption of molecules on the surface than is the case with S1. Tafel polarization showed that both Schiff bases are mixed corrosion inhibitors. The Temkin isotherm was found to provide an accurate description of the adsorption behavior of the Schiff bases. Calculation of thermodynamic parameters such as ΔGads0, ΔHads0 and ΔSads0 shows that the inhibitive action of the inhibitors is in the following order S1 < S2.

Inhibitive and Adsorption Properties of Ethanol Extract of Seeds and Leaves of Azadirachta Indica on the Corrosion of Mild Steel in H2SO4

The corrosion of mild steel in H 2SO 4 was studied using gravimetric, gasometric and IR methods. The results indicate that the rate of corrosion of mild steel in H 2SO 4 increases with increase in the concentration of the acid and that ethanol extracts of the seeds and leaves of Azadirachta indica inhibit the corrosion of mild steel in H 2SO 4. Inhibition efficiencies of the leaves and seeds extract range from 82.62 to 94.24% and from 60.55 to 84.78%, respectively. The inhibition potential of these extracts is attributed to the presence of tannin, saponin, glycoside, anthraquinone, flavonone and other phytochemicals in the extracts. IR study confirms that the inhibitors are adsorption inhibitors and the adsorption of the inhibitors on mild steel surface is exothermic, spontaneous and consistent with the assumptions of Flory-Huggins adsorption isotherm. Based on the values of the activation, free energy of adsorption and the variation of inhibition efficiency with temperature, a physical adsorption mechanism is proposed for the adsorption of ethanol extract of leaves and seeds of Azadirachta indica on the surface of mild steel.

Inhibitive action of some bipyrazolic compounds on the corrosion of steel in 1 M HCl : Part I: Electrochemical study

Potentiodynamic polarisation, electrochemical impedance spectroscopy and weight loss studies were carried out on the inhibition of carbon steel in 1 M hydrochloric acid solution by three bipyrazolic compounds. The examined inhibitors are 5,5′-dipropyl-1H,1′H-[3,3′]bipyrazolyl (Bp1), 5,5′-diphenyl-1H,1′H-[3,3′]bipyrazolyl (Bp2) and 5,5′-bis-(4-chloro-phenyl)-1H,1′H-[3,3′]bipyrazolyl (Bp3). All measurements show that inhibition efficiency increases with increase in inhibitor concentration and the variation in inhibitive efficiency mainly depends on the type and nature of the substituents present in the inhibitor molecule to attain 98% for chloro derivative (Bp3) at 10 −3 M. This reveals that inhibitive actions of bipyrazolic compounds were mainly due to adsorption on steel surface. Adsorption of these inhibitors follows Langmuir adsorption isotherm. Electrochemical impedance spectroscopy (EIS) measurements showed that the dissolution process of steel occurred under activation control. The curves of polarisation indicated that the examined inhibitors act primarily as cathodic inhibitors. From the adsorption isotherm, thermodynamic data for the adsorption process ( K, Δ G ads ° ) are calculated and discussed. Some quantum parameters (highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy and total partial charge of inhibitors atoms) are computed.