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The adsorption and inhibition effect of Ascorbyl palmitate (AP) on carbon steel in ethanol blended gasoline containing water as a contaminant (GE10+1%water) was studied by weight loss and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the addition of ethanol and water to gasoline increase the corrosion rate of carbon steel. AP inhibits the corrosion of carbon steel in (GE10+1% water) solution to a remarkable extent. The adsorption of AP on the carbon steel surface was found to obey the Langmuir adsorption isotherm model. The values of activation energy (Ea) and various thermodynamic parameters were calculated and discussed. © 2013 Elsevier Ltd.

Deyab M.A.,Egyptian Petroleum Research Institute
International Journal of Hydrogen Energy | Year: 2013

The purpose of this paper is to describe and evaluate the corrosion of carbon steel in crotonic acid for hydrogen production and using polysorbate 20 (NS), dioctyl sodium sulfosuccinate (AS) and benzalkonium chloride (CS) to control hydrogen evolution. Measurements were conducted in tested solutions using hydrogen evolution and electrochemical impedance spectroscopy (EIS) measurements and complemented by scan electron microscope (SEM) and energy dispersive X-ray (EDX) investigations. It is shown that the hydrogen generation rate obtained during the corrosion of carbon steel in crotonic acid increased with increase in acid concentration, temperature and immersion time. The addition of organic surfactants inhibits the hydrogen generation rate. The inhibition occurs through adsorption of organic surfactants on the metal surface. Adsorption processes followed the Langmuir isotherm. The order of effectiveness of the surfactants was AS > NS > CS. The values of activation energy (Ea) and heat of adsorption (Qads) were calculated and discussed. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Hegazy M.A.,Egyptian Petroleum Research Institute
Journal of Molecular Liquids | Year: 2015

Abstract The corrosion inhibition effect of novel cationic surfactant based on tolyltriazole on carbon steel in 7 M H3PO4 solution has been evaluated by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency increases with increasing inhibitor concentration, but it decreases with increasing the temperature. The adsorption of inhibitor is mixed physical and chemical adsorption and found to obey the Langmuir adsorption isotherm. Data obtained from EIS studies were analyzed to model inhibition process through appropriate equivalent circuit model. Potentiodynamic polarization studies have shown that the inhibitor acts as a mixed type of inhibitor. Scanning Electron Microscopy (SEM) study also confirmed the protection of the metal surface by the used cationic surfactant. © 2015 Elsevier B.V. All rights reserved.

Three cationic Schiff surfactants namely; N,N-dimethyl-4-(((1-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)methyl)-N-octylbenzenaminium bromide (APS-8); N,N-dimethyl-4-(((1-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)methyl)-N-dodecyl benzenaminium bromide (APS-12) and N,N-dimethyl-4-(((1-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)methyl)-N-hexadecylbenzenaminium bromide (APS-16) were synthesized and confirmed. The corrosion of carbon steel in 1.0 M HCl solution at 20-60 °C was studied by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results show that synthesized cationic surfactants are excellent inhibitors even with very low concentration, and the adsorption on carbon steel surface obeys Langmuir adsorption isotherm. Polarization curves reveal that the synthesized inhibitors behave as a mixed-type inhibitor. Adsorption of used inhibitors led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Thermodynamic and activation parameters were discussed. Calculated ΔG°ads values indicated that the adsorption mechanism of the prepared cationic surfactants on carbon steel in 1 M HCl solution is a chemical adsorption. © 2015 Elsevier B.V.

The effect of addition of carbon nanotubes (CNTs) on the corrosion resistance of conductive polymer coating (polyaniline) that coated aluminum bipolar plates in acidic environment inside the PEM fuel cell (0.1 M H 2SO4) was investigated using electrical conductivity, polarization and electrochemical impedance spectroscopy (EIS) measurements. Scanning electron microscopy (SEM) was used to characterize the coating morphology. The results show that the addition of CNTs to polyaniline coating enhanced the electrical conductivity and the corrosion resistance of polyaniline polymer. The inhibition efficiency of polyaniline polymer increased with increasing CNTs concentration. The best inhibition was generally obtained at 0.8% CNTs concentration in the acidic medium. This was further confirmed by decreasing the oxygen and water permeability and increasing coating adhesion in the presence of CNTs. EIS measurements indicated that the incorporation of CNTs in coating increased both the charge transfer and pore resistances while reducing the double layer capacitance. © 2014 Elsevier B.V. All rights reserved.

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