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Lebrini M.,French National Center for Scientific Research | Robert F.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Roos C.,Laboratoire Materiaux et Molecules en Milieu Amazonien
International Journal of Electrochemical Science | Year: 2010

In this work, an alkaloids extract from Annona squamosa plant have been studied as possible corrosion inhibitor for C38 steel in molar hydrochloric acid (1 M HCl). Potentiodynamic polarization and AC impedance methods have been used. The corrosion inhibition efficiency increases on increasing plant extract concentration. Polarisation studies showed that Annona squamosa extract was mixed-type inhibitor in 1 M HCl. The inhibition efficiency of Annona squamosa extract was temperature-dependent and its addition led to an increase of the activation corrosion energy revealing a physical adsorption between the extract and the metal surface. The adsorption of the Annona squamosa extract followed Langmuir's adsorption isotherm. The inhibitive effect of Annona squamosa is ascribed to the presence of organic compounds in the extract. The examined extract is considered as non-cytotoxic substance. © 2010 by ESG. Source


Lebrini M.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Roos C.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Vezin H.,CNRS Chemistry Laboratory | Robert F.,Laboratoire Materiaux et Molecules en Milieu Amazonien
International Journal of Electrochemical Science | Year: 2011

The inhibitive action of 9H-pyrido[3,4-b]indole (norharmane) and 1-Methyl-9H-pyrido[3,4-b]indole (harmane) on corrosion of C38 steel in 0.5 M H2SO4 solution was investigated through electrochemical techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution for all concentrations studied. Polarization measurements indicate that the examined compounds act as a mixed inhibitor and its inhibition efficiency increases with inhibitor concentration. Data obtained from ac impedance technique show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE), has been used. The adsorption of used compounds on the steel surface obeys Langmuir's isotherm. The ΔG°ads values were calculated and discussed for both inhibitors. Significant correlations are obtained between inhibition efficiency and quantum chemical parameters using quantitative structure-activity relationship (QSAR) method. © 2011 by ESG. Source


Lebrini M.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Robert F.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Roos C.,Laboratoire Materiaux et Molecules en Milieu Amazonien
International Journal of Electrochemical Science | Year: 2011

Corrosion inhibition effect of alkaloids extract from Palicourea guianensis plant (AEPG) on C38 steel in 1 M HCl medium has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The polarization studies showed that AEPG acts as mixed-type inhibitor. The electrochemical impedance spectroscopy showed that the charge transfer resistance increases and the double layer capacitance decreases on increasing plant extract concentration. The inhibition efficiency of the extract obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of the extract. Inhibition efficiency of 89% was achieved with 100 mg L-1 of AEPG at 25 °C. The obtained results showed that, the Palicourea guianensis extract could serve as an effective inhibitor for the corrosion of steel in acid media. The adsorption of AEPG obeys the Langmuir adsorption isotherm. © 2011 by ESG. Source


Lebrini M.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Robert F.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Vezin H.,CNRS Chemistry Laboratory | Roos C.,Laboratoire Materiaux et Molecules en Milieu Amazonien
Corrosion Science | Year: 2010

A comparative study of 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane) as inhibitors for C38 steel corrosion in 1. M HCl solution at 25. °C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behavior in the absence and presence of different concentrations of these inhibitors. The OCP as a function of time were also established. Cathodic and anodic polarization curves show that norharmane and harmane are a mixed-type inhibitors. Adsorption of indole derivatives on the C38 steel surface, in 1. M HCl solution, follows the Langmuir adsorption isotherm model. The ΔGads° values were calculated and discussed. The potential of zero charge (PZC) of the C38 steel in inhibited solution was studied by the EIS method, and a mechanism for the adsorption process was proposed. Raman spectroscopy confirmed that indole molecules strongly adsorbed onto the steel surface. The electronic properties of indole derivates, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR). © 2010 Elsevier Ltd. Source


Lebrini M.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Robert F.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Lecante A.,Laboratoire Materiaux et Molecules en Milieu Amazonien | Roos C.,Laboratoire Materiaux et Molecules en Milieu Amazonien
Corrosion Science | Year: 2011

The inhibition effect of alkaloids extract from Oxandra asbeckii plant (OAPE) on the corrosion of C38 steel in 1. M hydrochloric acid solution has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases on increasing plant extracts concentration. Cathodic and anodic polarization curves show that OAPE is a mixed-type inhibitor. The effect of temperature on the corrosion behavior of C38 steel in 1. M HCl with and without addition of plant extract was studied in the temperature range 25-55 °C. The thermodynamic functions of dissolution and adsorption processes were calculated from experimental polarization data and the interpretation of the results are given. The adsorption of this plant extract on the C38 steel surface obeys the Langmuir adsorption isotherm. Surface analysis (Raman) was also carried out to establish the corrosion inhibitive property of this plant extract in HCl solution. © 2010 Elsevier Ltd. Source

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