Electrochemical corrosion and inhibition mechanisms of galvannealed steel

10 páginas, 11 figuras, 2 tablas.[ES] Se ha estudiado el mecanismo de corrosión de un acero galvanorrecocido, en 0,6 M de cloruro sódico, mediante espectroscopia de impedancia electroquímica. Los resultados revelan que el sistema, para tiempos mayores de 48 h de inmersión y hasta 1 mes en NaCl, está controlado por un proceso de difusión en capa finita. A su vez, se ha estudiado la efectividad de sales de cerio como inhibidor añadido en el medio agresivo, obteniéndose porcentajes de inhibición del 85% para concentraciones de 500 y 1.000 ppm a las 24 h de exposición. Además, los espectros de impedancia electroquímica revelan un cambio en el mecanismo de corrosión del galvanorrecocido por la adición del cerio en el medio.[EN] The corrosion mechanism of galvannealed in 0,6 M NaCl has been evaluated by means of electrochemical impedance spectroscopy (EIS). After 48 hours and for longer immersion time, up to 1 month, in sodium chloride, the system is controlled by a diffusion process at finite layer. Moreover, the effectiveness of cerium salts as inhibitor added in the electrolyte has been studied. Inhibition percentages of about 85% for 500 and 1000 ppm at 24 hours have been found. On the hand, changes in the corrosion mechanism due to the cerium presence were shown.Peer reviewe

Corrosion protection of aluminium alloys by sol-gel coatings

[ES] En el presente trabajo se estudia la protección frente a la corrosión que proporcionan tres nuevos recubrimientos nanoméricos de baja temperatura de curado obtenidos a partir de silanos modificados. La síntesis de estos recubrimientos se realiza a partir de una mezcla de dos soles, GPTS (glicidoxipropiltrimetoxisilano) prehidrolizado y un segundo sol TEOS/MTES. Añadiendo a este sol inicial una disolución coloidal de partículas se obtienen recubrimientos nanoméricos de mayor espesor. En el presente trabajo los recubrimientos particulados se obtuvieron incorporando un 25% en peso de partículas comerciales de SiO2, Aerosil 300 y Aerosil R972 respectivamente. Una vez sintetizados, se depositaron mediante el método de centrifugado, sobre dos aleaciones de aluminio, 5555 y 3005 empleadas como substratos. El espesor final de los recubrimientos es de orden de 10 ìm, para el recubrimiento sin partículas y algo superiores, 12-14 ìm aproximadamente, para los recubrimientos con partículas. Los resultados electroquímicos indicaron que, en todos los casos, las muestras recubiertas presentaban una mejora en el comportamiento frente a la corrosión respecto de los substratos sin recubrir. La velocidad de corrosión disminuye 3 órdenes de magnitud para los recubrimientos con partículas y ésta disminución es algo inferior para aquellos que no contienen partículas.[EN] Present paper studies the corrosion protection of three new nanomeric coatings obtained from modified silanes and cured at low temperatures. The synthesis of these coatings is carried out starting from a mixture of two sols separately prepared: a prehydrolized GPTS (glicidoxipropiltrimetoxisilano) and a second sol TEOS/MTES. Adding to this initial sol a colloidal solution of 25% in weight of commercial particles of SiO2, Aerosil 300 and Aerosil R972 respectively can be obtained thicker nanomeric coatings. Once synthesized, they were deposited by means of the spin coating method onto two aluminum alloys, 5555 and 3005 used as substrates. The final thickness of the coatings is about 10 μm, for the coating without particles and slightly higher, 12-14 μm approximately, for the coatings with particles. The electrochemical results indicated that, in all cases, the coated samples presented an improvement in the corrosion behavior in comparison with bare alloys in aggressive media of NaCl. The corrosion rate decreased three orders of magnitude for the coatings with particles and lower for those that do not contain particles.Los autores quieren agradecer al proyecto BRITE BE-5111: "High Performance protection with sol-gel coatings on metals and enamels" por financiar parte de este estudio.Peer reviewe

Derecho y bienestar en animales de trabajo

Los animales han contribuido de manera fundamental con su trabajo al desarrollo de la sociedad. Desde los países más avanzados hasta los menos desarrollados, encontramos distintos tipos de actividades laborales en las que participan los animales. Pero a causa de la herencia cultural recibida, en la cual siempre han sido considerados y catalogados como meros objetos, propiedad de los seres humanos, se les ha impedido gozar nunca de ningún tipo de derechos en este ámbito. Este hecho se traduce en la ausencia de normas que determinen unas condiciones dignas en las que éstos desarrollen sus múltiples trabajos. En la actualidad existe una extensa legislación en materia de bienestar animal que podría ser extrapolada para crear un marco de protección de los animales en este ámbito. Por este motivo, se hace necesaria la creación de un protocolo que, a modo de guía, recoja y adapte la legislación ya existente para otros sectores y que junto a los principios y criterios que han sido descritos como piezas clave para garantizar el bienestar animal, sirva para establecer unos requisitos mínimos de obligado cumplimiento que deben marcar el desarrollo de cualquiera de las actividades de trabajo desarrolladas por animales.Animals have made a vital contribution towards developing of society. Both in less developed countries and in highly industrialized nations it can be found different types of work activities performed by animals. However, due to cultural conceptions considering the animals as mere objects of human property left them unable to enjoy their rights. What this means in practice is no the absence of norms that determine decent conditions in which these develop their multiple works. At present, there is a large amount of animal welfare legislation that could be extrapolated to create a framework for the protection of animals. It is, therefore, necessary to elaborate a protocol that, as a guide, collects and adapts all existing legislation in relation to the protection of animals while working. These principles and criteria have to be key elements to ensure animal welfare, defining the essential mandatory compliance that should mark the development of any work activity developed by animals

Early Triassic-Early Jurassic Bivalve Diversity Dynamics

Bivalves are a highly diversified molluscan class, with a long history dating from early Cambrian times (Cope, 2000). Although the group already showed a steady diversification trend during the Paleozoic, it only became highly successful and expanded rapidly from the Mesozoic onward. The Triassic was, for bivalves, first a recovery period and later a biotic diversification event. It was also the time bivalves first fully exploited their evolutionary novelties.Facultad de Ciencias Naturales y Muse

Early Triassic-Early Jurassic Bivalve Diversity Dynamics

Bivalves are a highly diversified molluscan class, with a long history dating from early Cambrian times (Cope, 2000). Although the group already showed a steady diversification trend during the Paleozoic, it only became highly successful and expanded rapidly from the Mesozoic onward. The Triassic was, for bivalves, first a recovery period and later a biotic diversification event. It was also the time bivalves first fully exploited their evolutionary novelties.Facultad de Ciencias Naturales y Muse

Biofacies analysis of Hettangian-Sinemurian bivalve/brachiopod associations from the Neuquén Basin (Argentina)

Based upon extensive sampling with strict stratigraphical control on Hettangian and Sinemurian deposits cropping out at the river Atuel region (southwest Mendoza Province), the presence of all bivalve and brachiopod genera was recorded. Data gathered from the analysed interval were processed by multivariate analysis and the resulting Q-mode dendrogram was used to discriminate five associations (i.e. Entolium-limoids, Pholadomya-Pinna-Pleuromya, Weyla-Gryphaea, Lywea and Cardinioides). These are not in simple stratigraphical succession but are recurrent, reflecting palaeosynecological and biofacies influences. The palaeoenvironmental implications of these associations are analysed, as well as their geographical and stratigraphical distributions in the studied sections (Arroyo Malo, El Pedrero and Las Chilcas). The Cardinioides association is controlled by palaeosalinity and corresponds to a paralic/estuarine environment, of restricted geographical and stratigraphical distribution, whereas the remaining associations correspond to normal marine shelf to littoral environments. The Lywea association is interpreted as allochthonous and probably an impoverished subset derived from the diverse Weyla-Gryphaea association. On the basis of the palaeoautecological characteristics of the taxa involved in terms of guilds represented in these benthonic associations, it is concluded that most of the associations were dominated by the epifauna, whereas in the Pholadomya-Pinna-Pleuromya association the infauna and semi-infauna were particularly conspicuous and diverse, and the Cardinioides association was characterized by shallow infauna. Typical basinal biofacies from deeper, off-shore environments, and fresh-water biofacies, are both missing

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay river and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Paraná Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.Facultad de Ciencias Naturales y Muse

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay river and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Paraná Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.Facultad de Ciencias Naturales y Muse

Colección helmintológica del Museo de La Plata: I. catálogo de preparaciones microscópicas, material tipo y no tipo

Slides refered to 106 helminth species, 11 Temnocephala, 1 Aspidogastrea, 11 Monogenes, 77 Digenea, 5 Cestoda and 1 Acanthocephala, held in the La Plata Museum helminthological collection are ctalogued. Species are organized according to their main taxonomic group and listed alphabetically according to the their original name. The registration number, indication of type rank, host, localization, locality is included. The original biliographic references where the specimens have been described are given, and when necesary supplementary references added. last, the cataloque is complemented with alphabetical list of 70 genera, of 100 helminth species and the 104 hosts included. In complience with Reccomentation 72D od the International Code of Zoological Nomeclature this catalogue includes type specimens in this collection aa no previous one has ever been published.Facultad de Ciencias Naturales y Muse

Colección helmintológica del Museo de La Plata: I. catálogo de preparaciones microscópicas, material tipo y no tipo

Slides refered to 106 helminth species, 11 Temnocephala, 1 Aspidogastrea, 11 Monogenes, 77 Digenea, 5 Cestoda and 1 Acanthocephala, held in the La Plata Museum helminthological collection are ctalogued. Species are organized according to their main taxonomic group and listed alphabetically according to the their original name. The registration number, indication of type rank, host, localization, locality is included. The original biliographic references where the specimens have been described are given, and when necesary supplementary references added. last, the cataloque is complemented with alphabetical list of 70 genera, of 100 helminth species and the 104 hosts included. In complience with Reccomentation 72D od the International Code of Zoological Nomeclature this catalogue includes type specimens in this collection aa no previous one has ever been published.Facultad de Ciencias Naturales y Muse