Sildenafil citrate (Viagra) as a corrosion inhibitor for carbon steel in hydrochloric acid solutions

Abstract  

The inhibition effect of sildenafil citrate (Viagra) on the corrosion of carbon steel in 1 M HCl was studied by weight loss, polarization, electrochemical impedance spectroscopy, and UV–Vis spectrophotometry. The results showed that sildenafil citrate is a good corrosion inhibitor for carbon steel in acidic media and acts as mixed type (cathodic/anodic) inhibitor. The adsorption of the inhibitor was well described by the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy, and adsorption free energy were calculated. Kinetic parameters such as the apparent activation energy and pre-exponential factor were calculated and discussed.     

Poly(4-vinylpyridine-hexadecyl bromide) as corrosion inhibitor for mild steel in acid chloride solution

The influence of the addition of poly(4-vinylpyridine-hexadecyl bromide) P4VP-Alkyl 50?% newly synthesized on the corrosion of mild steel in molar hydrochloric acid has been investigated by weight-loss measurements combined with linear potential scan voltammetry (I?CE) and electrochemical impedance spectroscopy (EIS). The polymer reduces the corrosion rate and the inhibition efficiency (E?%) of P4VP-Alkyl 50?% increases with its concentration and attains 95?% at 300?mg/L. E?% obtained from cathodic Tafel plots, EIS, and gravimetric methods were in good agreement. The inhibitor was adsorbed on the iron surface according to the Langmuir adsorption isotherm model. Polarization measurements also show that the compound acts as a cathodic inhibitor.     

Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5 M H2SO4 solution

A study on the use of the methanol extract of Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5?M of sulfuric acid has been carried out by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and gravimetric tests. Testing temperatures were 25°C, 40°C and 60°C. Results showed that M. sativa is a good corrosion inhibitor, with its efficiency increasing with its concentration and with time, but decreasing with the temperature. M. sativa forms a passive film on top of the steel with a passive current density and pitting potential values lower than that for uninhibited solution, and remained on the steel for 8–12?h. This film formed by iron ions and heteroatoms present in OH^? and amine groups from the extract are adsorbed on the steel and form a protective film on to the steel.     

Spectral and thermal studies of some 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives

A spectral study (IR and UV spectroscopies) of seven 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives has been carried out. The thermal study of the compounds allowed us to characterize the following processes: (i) desolvations, (ii) solid-solid transitions, (iii) melting, (iv) pyrolytic decompositions. Through the IR spectral study it was established that pyrolytic decompositions of all the compounds start with the acetyl groups. The reaction orders and activation energies of the deacetylation processes have been calculated.     

Spectral and thermal studies of copper(II) complexes of 3- and 4-pyridinealdoxime

Copper(II) complexes of 3- and 4-pyridinealdoxime have been prepared and analyzed by spectroscopic (ir and diffuse reflectance) and thermoanalytical (TG, DTG and DTA) techniques. For both these systems, only species with metal: organic ligand: chloride ratio of 122 were found, and the organic ligand appears as a neutral molecule. The spectral data suggest a polymeric structure where the copper(II) ions are in a distorted octahedral environment.The thermal decompositions occur through the reduction of copper(II) to copper(I) and the conversion of the residual organic ligand into acid amide, as found for dihydrogenbis(pyridine-2-aldoxime) copper(II) chloride, but the initial decomposition temperatures are slightly increased, giving rise to the thermal stability sequence:

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Zusammenfassung Kupfer(II)-Komplexe von 3- und 4-Pyridinaldoxim wurden hergestellt und spektroskopisch (IR und diffuse Reflexion) sowie thermoanalytisch (TG, DTG und DTA) analysiert. Für beide Systeme wurden nur Species mit einem Metall:Ligand:Chlorid-Verhältnis von 122 gefunden. Der organische Ligand liegt als neutrales Molekül vor. Die Spektren deuten auf eine polymère Struktur hin, in der die Kupfer(II)-Ionen in einer verzerrten oktaedrischen Koordination vorliegen. Die thermischen Zersetzungen verlaufen über die Reduktion von Cu(II) zu Cu(I) und die Umwandlung des verbleibenden organischen Liganden in Säureamid, wie für Dihydrogen-bis(pyridin-2-aldoxim)-kupfer(II)-chlorid gefunden wurde, aber die Temperaturen des Beginns der Zersetzung und damit die thermische Stabilität steigen in der Reihenfolge [Cu(Py₄-CHNOH)₂Cl₂][Cu(Py₃-CHNOH)₂Cl₂]>[Cu(Py₂-CHNOH)₂]Cl₂ etwas an.

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(, ) ( ) 3- 4- . 122, . , . -( -2-)- . , , , : Cu(4-Py-CHNOH)₂Cl₂Cu(3-Py-CHNOH)₂Cl₂>Cu(2-Py-CHNOH)₂Cl₂.

     

Synthesis,characterization and study of methyl 3-(2-oxo-2H-1,4-benzoxazin-3-yl) propanoate as new corrosion inhibitor for carbon steel in 1M H2SO4 solution

Research on Chemical Intermediates - A new benzoxazin derivative, namely methyl 3-(2-oxo-2H-1,4-benzoxazin-3-yl) propanoate (1,4-MBXP), was synthesized under mild conditions from 2-aminophenols and...     

4-{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitirle and Phthalocyanines Thereof

Russian Journal of General Chemistry - 4{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitrile was synthesized by diazotization and azo coupling and used to prepare...     

Synthesis of (2-hydroxo-5-chlorophenylaminoisonitrosoacetyl)phenyl ligands and their complexes: Spectral,thermal and solvent-extraction studies

Four different types of new ligands Ar[COC(NOH)R] _n (Ar=biphenyl, n = 1 H₂L¹; Ar=biphenyl, n = 2 H₄L²; Ar=diphenylmethane, n = 1 H₂L³; Ar=diphenylmethane, n = 2 H₄L⁴; R=2-amino-4-chlorophenol in all ligands) have been obtained from 1 equivalent of chloroketooximes Ar[COC(NOH)Cl] _n (HL¹-H₂L⁴) and 1 equivalent of 2-amino-4-chlorophenol (for H₂L¹ and H₂L³) or 2 equivalent of 2-amino-4-chlorophenol (for H₄L² and H₄L⁴). (Mononuclear or binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized with these ligands.) These compounds have been characterized by elemental analyses, AAS, infra-red spectra and magnetic susceptibility measurements. The ligands have been further characterized by ¹H NMR. The results suggest that the dinuclear complexes of H₂L¹ and H₂L³ have a metal:ligand ratio of 1:2; the mononuclear complexes of H₄L² and H₄L⁴ have a metal:ligand ratio of 1:1 and dinuclear complexes H₄L² and H₄L⁴ have a metal:ligand ratio of 2:1. The binding properties of the ligands towards selected transition metal ions (Mn^II, Co^II, Ni^II, Cu^II, Zn^II, Pb^II, Cd^II, Hg^II) have been established by extraction experiments. The ligands show strong binding ability towards mercury(II) ion. In addition, the thermal decomposition of some complexes is studied in nitrogen atmosphere.     

Synthesis and thermal reaction of 2-perfluoropropyl or (2-pyridyl)-5-phenyl-6-[4-(4-ethynylphenoxy) phenyl] -as-triazine

4-(4-Ethynylphenoxy) benzil was separately reacted with two amidrazones to provide acetylene-containing phenyl-as-triazine products. Each product consisted of two isomers which were separated by high pressure liquid chromatography and analyzed by mass spectroscopy. Differential scanning calorimetry was employed to study the thermal reaction of the acetylene-containing phenyl-as-triazine products. The principal component from the thermally induced reaction of the acetylene-containing phenyl-as-triazine was identified by mass spectroscopy as a dimer.     

Spectral, analytical, thermal, and antimicrobial studies of novel sodium 2-[4(2-hydroxy-3-izopropylaminopropoxy)phenyl]acetamide (atenolol) dithiocarbamate and its divalent transition metal complexes

Atenolol dithiocarbamate (ADTC) and its complexes with Cu(II), Co(II), Ni(II), Zn(II), and Cd(II) have been synthesized. These newly synthesized products have been characterized by elemental analyses (C, H, N, and S), thermal (thermogravimetry (TG) and differential thermal analyses (DTA)) as well as by spectral (UV, IR, and NMR (¹H)) studies. The stability constants (β) of metal complexes of ADTC have been determined by UV-Vis data in solutions in DMSO. The antimicrobial activities of the metal complexes have been screened in vitro against ten bacteria. The text was submitted by the authors in English.     

Spectral Response to Protonation of 4-(4-(4-(Didodecylamino)phenylazo)phenyl)butyric Acid in Its Langmuir-Blodgett Monolayer

4-(4-(4-(Didodecylamino)phenylazo)phenyl)butyric acid is synthesized, and its Langmuir-Blodgett (LB) monolayer is successfully fabricated. The drastic changes in electronic spectra of this compound are found in acidic solution and in LB monolayer upon exposure to HCl vapor (mainly the decrease in absorption at 416 nm and great increase at 540 nm). The UV-visible and infrared spectra reveal a mechanism of protonation to either azo group or amino group. This phenomenon has been suggested to have its prospective application in fundamental interfacial materials for pH sensors. Copyright 2000 Academic Press.     

Stereochemical studies of 5-methyl-3-(substituted phenyl)-5-[(substituted phenyl) hydroxy methyl]-2-thiooxazolidin-4-ones

The synthesis and stereochemical aspects of the aldol products, 5-methyl-3-(substituted phenyl)-5-[(substituted phenyl) hydroxy methyl]-2-thiooxazolidin-4-ones, are discussed.     

4-phenyl-decahydro-1H-1,5-benzodiazepin-2-one as novel and effective corrosion inhibitor for carbon steel in 1 M HCl solution: A combined experimental and empirical studies

The heterocyclic system, namely 4-phenyl-decahydro-1H-1,5-benzodiazepin-2-one (POBZ) was inspected as a corrosion inhibitor of carbon steel (CS) in a 1 M HCl medium through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements (PDP), and scanning electron microscopy (SEM). The experimental data indicate that the inhibiting action augments with augmenting POBZ amount and reduces with augmenting temperature. The inhibiting action efficiency of 90.98% is obtained with 0.001 M at 303 K. The potentiodynamic polarization (PDP) results mentioned that the POBZ is of mixed type. The adsorption of POBZ on the CS followed Langmuir isotherm. SEM exams affirmed that the steel surface is smooth in presence of POBZ. In light of the calculations of density functional theory (DFT) and molecular dynamics simulation, the mechanism of POBZ inhibitory activity was addressed.     

meso-四[(4-苯乙烯氨基)苯基]卟啉合成及其波谱特点

以吡咯和对硝基苯甲醛为原料,经过环化、还原和缩合,合成了meso-四[(4-苯乙烯氨基)苯基]卟啉(TBAPP),通过UV-Vis、FT-IR、1H NMR及元素分析等对产物进行了表征,并对其荧光和电子顺磁共振特性进行了研究。 卟啉产物的EPR测定显示出游离基特征,表明卟啉分子的大π共轭结构对周边基团产生的自由基有稳定作用。 取代基对卟啉的紫外 可见吸收、光致发光及电子顺磁共振特性均有影响。 四席夫碱苯基卟啉TBAPP的Q带比前体四氨基卟啉（TAPP）和母体四硝苯基卟啉（TNPP）红移,而Soret谱带变化较小;TBAPP的440 nm光激发的最大荧光峰658 nm分别比TAPP蓝移5 nm和比TNPP红移9 nm;TBAPP的EPR精细结构比TAPP弱,而比TNPP强。     

Assessment of inhibitory behavior of ethyl 5-cyano-4-(furan-2-yl)-2-methyl-6-oxo-1,4,5,6-tetrahydropyridine-3-carboxylate as a corrosion inhibitor for carbon steel in molar HCl: Theoretical approaches and experimental investigation

The new ethyl 5-cyano-4-(furan-2-yl)-2-methyl-6-oxo-1,4,5,6-tetrahydropyridine-3-carboxylate (THP) has been studied to prevent the electrochemical decomposition of carbon steel in an acidic medium used in the production process using electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy), weight reduction methods and surface morphological. Computational correlations (DFT and molecular dynamics simulations) were carried out to have more information on the mechanism of inhibition. Experimentally obtained results revealed that the inhibition efficiency increases with the concentration, and the highest effectiveness is reached for 10^?3M, with 95.22%, and the compound is classified as a mixed inhibitor. Indeed, the increase in temperature caused an increase in the values of i_corr throughout the studied temperature range. Moreover, the obtained results showed that the adsorption on carbon steel is accomplished according to the Langmuir adsorption model and the adsorption parameters reflect that the THP is spontaneously adsorbed by physical adsorption, which increases the barrier energy required for the corrosion reaction. The theoretical approaches used show that THP suggests a perfect adsorption by all its chemical structure.     

Inhibitive,adsorption and synergistic studies on ethanol extract of Gnetum Africana as green corrosion inhibitor for mild steel in H2SO4

Abstract

The inhibitive and adsorptive characteristics of ethanol extract of Gnetum Africana for the corrosion of mild steel in H₂SO₄ solutions have been studied using weight loss, gasometric, thermometric, and IR methods of monitoring corrosion. Ethanol extract of Gnetum Africana is a good adsorption inhibitor for the corrosion of mild steel in H₂SO₄. The inhibitive property of the extract is attributed to the presence of alkaloid, saponin, tannin, terpene, anthraquinone, cardiac glycoside, and alkaloid in the extract. The adsorption of the inhibitor on mild steel surface is exothermic, spontaneous and is consistent with the mechanism of physical adsorption. In addition, Langmuir and Temkin adsorption isotherms best described the adsorption characteristics of the inhibitor. Efforts to improve the adsorption of the inhibitor through synergistic combinations with halides indicated that only KCl may enhance the efficiency of the inhibitor. The study provides information on the use of ethanol extract of Gnetum Africana as a corrosion inhibitor for mild steel.     

1-Phenacylmethyl-2-(acylaminothiocarbonylamino)pyridinium bromides as protectors of steel acid corrosion

Inhibiting effect of 1-phenacylmethylpyridinium bromides containing acylthiourea substituents in the pyridine ring on corrosion of mild steel in sulfuric acid (3 M) was studied.     

Spectral and thermal studies of Y(III) and heavy lanthanide 4-chlorophthalates

Summary Complexes of heavy lanthanide(III) (Gd-Lu) and Y(III) with 4-chlorophthalic acid were prepared and their IR spectra, solubility in water at 295 K and thermal decomposition were investigated. When heated the complexes with general formula Ln₂[ClC₆H₃(CO₂)₂]₃·nH₂O where n=6 for Tb, Dy(III), n=4 for Gd, Ho and Er(III), n=2 for Tm-Lu(III) and n=3 for Y(III) decompose to the oxides Ln₂O₃, Tb₄O₇ with intermediate formation of oxochlorides LnOCl.     

Synthesis of 2,2-dialkyl(phenyl)-4-(2-hydroxyethyl)thiadiazinones

2,2-Dialkyl(phenyl)-4-(2-hydroxyethyl)thiadiazin-5-ones are formed as a result of the reaction of thioglycolic acid with 2-hydroxyethylhydrazones. The structures of the reaction products were proved by PMR and ¹³C NMR spectrometry and the mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 838–839, June, 1991.