Temperature Effect on the Corrosion Inhibition of Carbon Steel by Polymeric Ionic Liquids in Acid Medium.

In the present research work, the temperature effect on the corrosion inhibition process of API 5L X60 steel in 1 M H2SO4 by employing three vinylimidazolium poly(ionic liquid)s (PILs) was studied by means of electrochemical techniques, surface analysis and computational simulation. The results revealed that the maximal inhibition efficiency (75%) was achieved by Poly[VIMC4][Im] at 308 K and 175 ppm. The PILs showed Ecorr displacements with respect to the blank from -14 mV to -31 mV, which revealed the behavior of mixed-type corrosion inhibitors (CIs). The steel micrographs, in the presence and absence of PILs, showed less surface damage in the presence of PILs, thus confirming their inhibiting effect. The computational studies of the molecular orbitals and molecular electrostatic potential of the monomers suggested that the formation of a protecting film could be mainly due to the nitrogen and oxygen heteroatoms present in each structure.

Investigation of Sulfonium-Iodide-Based Ionic Liquids to Inhibit Corrosion of API 5L X52 Steel in Different Flow Regimes in Acid Medium.

The present work deals with the corrosion inhibition mechanism of API 5L X52 steel in 1 M H2SO4 employing the ionic liquid (IL) decyl(dimethyl)sulfonium iodide [DDMS+I-]. Such a mechanism was elicited by the polarization resistance (R p), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques, both in stationary and dynamic states. The electrochemical results indicated that the corrosion inhibition was controlled by a charge transfer process and that the IL behaved as a mixed-type corrosion inhibitor (CI) with anodic preference. The experimental results revealed maximal inhibition efficiency (IE) rates up to 93% at 150 ppm in the stationary state, whereas in turbulent flow, the IE fell to 65% due to the formation of microvortexes that promoted higher desorption of IL molecules from the surface. The Gibbs free energy of adsorption (ΔG°ads) value of -34.89 kJ mol-1, obtained through the Langmuir isotherm, indicated the formation of an IL monolayer on the metal surface by combining physisorption and chemisorption. The surface analysis techniques confirmed the presence of Fe x O y , FeOOH, and IL on the surface and showed that corrosion damage diminished in the presence of IL. Furthermore, the quantum chemistry calculations (DFT) indicated that the iodide anion hosted most of the highest occupied molecular orbital (HOMO), which eased its adsorption on the anodic sites, preventing the deposition of sulfate ions on the electrode surface.

Inhibition Mechanism of Some Vinylalkylimidazolium-Based Polymeric Ionic Liquids against Acid Corrosion of API 5L X60 Steel: Electrochemical and Surface Studies.

A corrosion inhibition mechanism of API 5L X60 steel exposed to 1.0 M H2SO4 was proposed from the evaluation of three vinylalkylimidazolium poly(ionic liquids) (PILs), employing electrochemical and surface analysis techniques. The synthesized PILs were classified as mixed-type inhibitors whose surface adsorption was promoted mainly by bromide and imidazolate ions, which along with vinylimidazolium cations exerted a resistive effect driven by a charge transfer process by means of a protective PIL film with maximal efficiency of 85% at 175 ppm; the steel surface displayed less surface damage due to the formation of metal-PIL complex compounds.

Caracterización de la prescripción de antihistamínicos en la consulta externa de un Hospital Nacional / Characterization of the prescription antihistamine in the outpatient unit of a National Hospital

El presente trabajo es un estudio descriptivo cuyo objetivo fue la caracterización de la prescripción de los antihistamínicos en la Consulta Externa en un hospital clase A, nacional, para adultos, de nuestro país; se estudiaron las recetas de antihistamínicos despachadas por el servicio de farmacia durante los meses de enero, febrero y marzo del año 2006. El Servicio de Farmacia del hospital estudiado durante el período despachó a 9260 recetas de antihistamínicos provenientes de la consulta externa. El antihistamínico con mayor prescripción fue el clorhidrato de fexofenadina, la cantidad prescrita superó dos veces la cantidad de hidroxicina, segundo antihistamínico de mayor prescripción. En un 12,75 por ciento del total de las recetas estudiadas se encontró la asociación de fexofenadina con otro antihistamínico de primera generación. El antihistamínico de primera generación que se asoció principalmente con la prescripción de fexofenadina fue hidroxicina, 64,4 por ciento, seguida de clorfeniramina, 30.6 por ciento y difenhidramina, 5.1 por ciento. Se tiene un costo estimado de 9369335.28; de este monto, al menos una cantidad cercana a los 443022.60 fue utilizada en la prescripción de antihistamínicos de primera generación, en forma conjunta con el clorhidrato de fexofenadina...