Pulsed Laser Deposition in a Zinc Alloy Corrosion Study
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Pulsed Laser Deposition in a Zinc Alloy Corrosion Study R. Guerrero-Penalva, M.H. Faríasb and L. Cota-Araizab Instituto Tecnológico de Tijuana, Centro de Graduados e Investigación, Apartado Postal 1166, Tijuana, BC 22000, México. [email protected] b Centro de Ciencias de la Materia Condensada de la UNAM, Apartado Postal 2681, Ensenada, BC 22800, México. [email protected], [email protected], Fax +++52-6-1744603 ABSTRACT A significant improvement in corrosion resistance of the protecting oxide of alloys has been observed when adding small amounts of reactive elements, such as yttrium, this effect has been called reactive element effect (REE). The general mechanism of the REE has not been determined yet. In this work, we study a growing of a yttrium oxide film and its interaction with the phases η and α that constitutes the alloy Zn-22Al-2Cu named Zinalco. The alloy’s surface was coated by a pulsed laser deposition technique. The deposit is controlled and characterized by x-ray photoelectron spectroscopy. The mechanism by which the reactive element produce its effects in this alloy is explained by the preferential interaction among the active sites related to the zinc rich phase and enhancing aluminum movement toward the surface where it is oxidized and the protection film formed. IINTRODUCTION A significant improvement in corrosion resistance of the protective oxides of alloys has been observed when adding small amounts of other elements, such as yttrium. Pfeil [1] demonstrated and patented a treatment in 1937 where adding yttrium oxide to a Cr-Ni alloy, caused a drastic improvement in oxidation and exfoliation resistance during cyclic heating and cooling. This effect was named reactive element effect (REE). According to some recent review articles [2], REE studies have been performed on alloys containing iron, cobalt or nickel as metal base. In general, accomplished on alloys under a broad commercial use with the common characteristic of aluminum or chromium as alloying metal. These last two metals are the best in forming protective oxide films. Little or nothing has been published about the REE produced improvements on alloys based on magnesium [3] or zinc. Several particular mechanisms, which can be applied to certain specific cases, have been proposed. However, the general mechanism of the REE has not been determined yet. The REE can be obtained by incorporating either metallic yttrium or a dispersion of oxide particles [4]. One of the assertions by Pfeil in his original article for the REE patent is that the beneficial effect could be obtained by means of surface coatings with the reactive element. Several surface deposition techniques have been used to obtain the REE, such as: ion implantation [5], fusion of the reactive element with substrate by laser cladding [6], immersion of reactive element in nitrate aqueous solutions [7], sol-gel method by immersion or electroforesis [8], reactive sputtering [9] and electrochemical deposition from organic nitrate solutions [10]. To our best knowledge, REE stu
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