Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

Tinplate is used to food packaging and other types of packages. The corrosion resistance of the tinplate has been study due the necessity of an alternative to high environmental impact of chromatization process. Therefore protective coatings as hybrid films base elaborations with different acids are studied to improve the barrier effect against corrosion. The objective of this work is characterize hybrid films deposited on a tinplate from a sol made up of the alkoxide precursors 3-(trimethoxysilylpropyl) methacrylate (TMSM), tetraethoxysilane (TEOS) and poly(methyl methacrylate) (PMMA) together with one of three acids (acetic, hydrochloric or nitric acid) and to verify their action against the corrosion of the substrate. The films were obtained by a dip-coating process and cured for 3 hours at 160 °C. The film hydrophobicity was determined by contact angle measurements, and the morphology was evaluated by SEM. FTIR measurements were performed to characterize the chemical structures of the films. The electrochemical behavior of the coatings was evaluated by techniques open circuit potential monitoring (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results demonstrate that the siloxane-PMMA films improve the protective properties of the tinplate, with the films obtained by acetic acid addition exhibiting the greatest improvement

THE ADDITIONAL DETERMINATION OF THE PHASE DIFFERENCE IN REFLECTION SPECTROSCOPY

Des phases intermédiaires, ayant une anisotropie uniaxiale, sont caractérisées par les parties réelles et imaginaires des intégrales [MATH] Ces résultats sont obtenus par application stricte de la théorie de continuum de Maxwell pour le cas d'une frontière de phase perturbée utilisant des conditions intégrales de limite. Pour la détermination complète de ces quantités, quatre valeurs expérimentales sont nécessaires. Celles-ci sont les réflectivités ƊR/R et les différences de phase Ɗφ qu'on peut obtenir à l'aide de la spectroscopie de réflexion avec de la lumière polarisée parallèlement et perpendiculairement. La méthode mathématique des transformations de type "Kramers-Kronig" et la détermination expérimentale de Ɗφ par interférométrie sont décrites. L'application de la méthode "Kramers-Kronig" est démontrée pour le cas des couches d'oxyde de platine sur Pt et pour l'adsorption de rhodamine B sur Pt et Ag. Pour le cas du système oxyde de platine sur Pt la componente tangentielle [MATH] et la componente normale [MATH] de [MATH] sont déterminées en plus. Dans le cas de couches organiques adsorbées, les intégrales sont discutées en tenant compte de l'orientation des molécules organiques sur la surface.It follows from a derivation of Fresnel's reflection coefficients using integral boundary conditions that within the framework of the Maxwell continuum theory four quantities can be determined for an interface with uniaxial anisotropy. These quantities are the real and imaginary parts of the integrals [MATH] ([MATH] = tangential component, [MATH] normal component of the dielectric constant tensor, [MATH] dielectric constant of the reference state). To determine these quantities four experimental values are necessary. These values can be obtained by the additional determination of the phase change Ɗφ in reflection spectroscopy with parallel and perpendicular polarized light. The Kramers-Kronig transformation method and the possible measurement of Ɗφ by interferometry are described. Examples for the Kramers-Kronig transformation method are the determination of the phase change during reflection Ɗφ for platinum oxide layers on Pt and for rhodamin B adsorption layers on Pt and Ag. From ƊR/R and Ɗφ the integrals are calculated. In the case of platinum oxide on Pt additionally the tangential and normal component of [MATH] are derived. In the case of the organic adsorption layers the integrals are discussed with regard to the orientation of the organic molecules on the surface

Bond Energies in Alloys Determined from Underpotential Deposition Potentials

A procedure is presented to determine bond energies between the metal (Me) and substrate (S) components of binary alloys from characteristic underpotential deposition (UPD) potentials. The bond energy between Me and S atoms is one of the factors governing the deposition kinetics and structure of Me-S alloy deposits. The proposed procedure is based on the determination of the UPD potential for formation of a condensed two-dimensional (2D) phase of the less noble metal Me (the UPD metal) on the more noble metal S (the substrate). Making reasonable approximations, the sublimation enthalpy of the condensed 2D Me phase is obtained from the corresponding formation underpotential. From this sublimation enthalpy the bond energy of an atom of the UPD metal in a kink site position of the 2D Me phase is calculated. This value is used to calculate the bond energy (phi(Me-S)) between an Me atom and an S atom. The method is demonstrated using experimental data obtained in selected electrochemical UPD systems