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Search Results: 1 - 10 of 450500 matches for " Oladis T de Rincón "
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Efecto de los iones ferrosos, el pH y el H2S a nivel de interfase en el mecanismo de corrosión del hierro por bacterias sulfato-reductoras Influence of ferrous ions, pH and H2S at the interface on the corrosion mechanism of iron by Sulfate-Reducing Bacteria
Lisseth Ocando,Matilde Fernández de Romero,Orlando Pérez,Oladis T de Rincón
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: La Corrosión Inducida Microbiológicamente (MIC) por Bacterias Sulfato-Reductoras (BSR) es un fenómeno que acarrea graves da os para muchas industrias y sistemas. Numerosas teorías se han formulado para explicar los mecanismos que gobiernan MIC y, recientemente, ha sido propuesto un mecanismo de corrosión del hierro por estas bacterias. En este mecanismo se ha establecido que los sulfuros de hierro precipitados son los que propician el proceso corrosivo del acero, junto con el H2S generado por las BSR, y supone que, por la actividad metabólica de las mismas, en la interfase metal/solución ocurre un descenso del pH que acelera el proceso corrosivo de forma localizada. Por tanto, el objetivo principal de esta investigación consistió en evaluar el pH a nivel de interfase metal/solución, tanto en medios con iones ferrosos (al igual que en el mecanismo) como en ausencia de ellos, con el propósito de verificar la ocurrencia de esta acidificación y determinar la influencia de estos iones en el proceso corrosivo. También, evaluar la concentración deH2S a nivel de interfase y determinar su relación con el pH. Para medir estos dos parámetros durante 24 horas en ambos medios, se utilizó microelectrodos de pH y H2S. Por otro lado, se determinó la morfología de biopelícula y de ataque en los dos medios de cultivo mediante microscopía electrónica de barrido (MEB). Los resultados arrojaron que el pH disminuye a nivel de interfase metal/solución dependiendo de la presencia de iones ferrosos. Adicionalmente, con esta investigación se confirmó la influencia adversa de los iones Fe++ y la agresividad de los sulfuros de hierro en el proceso corrosivo. Microbiologically Influenced Corrosion (MIC) by Sulfate-Reducing Bacteria (SRB) has been the subject of extensive studies for the past five decades and several theories have been proposed to explain the mechanisms governing MIC. Recently, a corrosion mechanism for the action of SRB on iron was proposed, which seeks to explain the initiation of this kind of corrosion in order to improve prevention and mitigation techniques. This mechanism was supported on the fact that there should be a local pH decrease at the metal/solution interface. So, the principal aim of this work was to prove this theory by evaluating an iron interface exposed to a culture medium rich in nutrients and SRB. The H2S concentration produced was also evaluated to establish its relation with the pH at the interface. To measure these parameters during 24 hours, pH and H2S microelectrodes with tip diameters of 10 μm were used. A SRB pure culture of Desulfovibri
Designing a computarized mathematical model corrosion costs
de Romero,Matilde E; Aponte,Bertila; Arias,Silagdy; de García,Francisca F; de Rincón,Oladis T; Larreal,Oswaldo;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2005,
Abstract: recording and analyzing the costs associated with corrosion control in venezuelan industry, indeed in most industries, is not considered as a factor associated with an individual or independent heading under corrosion. they are simply listed or included under general maintenance operations, which conceals the costs really incurred by corrosion. the need therefore arises for segregating these costs so as to be able to determine not only how much industry invests with respect to this problem but also how it impacts its budgets and the losses sustained as a function of the gross domestic product (gdp). these costs were determined by first developing a phase in which a series of surveys and interviews were carried out among the industries that are most important for the venezuelan economy, considering two of the main categories in the industrial sector: production-manufacture and services. secondly, a computerized mathematical model was developed from the series of variables produced by these instruments. the model includes all the essential variables associated with corrosion problems and control methods. the application of this model will provide knowledge of the costs associated with the problem of corrosion in venezuela at large as well as in the industries in which it is applied.
Influence of ferrous ions, pH and H2S at the interface on the corrosion mechanism of iron by Sulfate-Reducing Bacteria
Ocando,Lisseth; Fernández de Romero,Matilde; Pérez,Orlando; de Rincón,Oladis T; Duque,Zoilabet; León,Ennery; Atencio,Laura; Ortiz,Reynaldo;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: microbiologically influenced corrosion (mic) by sulfate-reducing bacteria (srb) has been the subject of extensive studies for the past five decades and several theories have been proposed to explain the mechanisms governing mic. recently, a corrosion mechanism for the action of srb on iron was proposed, which seeks to explain the initiation of this kind of corrosion in order to improve prevention and mitigation techniques. this mechanism was supported on the fact that there should be a local ph decrease at the metal/solution interface. so, the principal aim of this work was to prove this theory by evaluating an iron interface exposed to a culture medium rich in nutrients and srb. the h2s concentration produced was also evaluated to establish its relation with the ph at the interface. to measure these parameters during 24 hours, ph and h2s microelectrodes with tip diameters of 10 μm were used. a srb pure culture of desulfovibrio desulfuricans subs. desulfuricans was used, grown as batch culture in modified atcc 1249 medium with and without ferrous ions, in order to determine their influence on the ph and h2s behavior. attack morphology and biofilm structure in both mediums were also determined by scanning electron microscopy (sem). the results showed that ph into the biofilm decreased depending on the ferrous ions presence. also, it was confirmed the influence of ferrous ions and ferrous sulfides aggressiveness in the corrosion process established in the mechanism.
The atmospheric corrosivity maps in Zulia region
Rincón,álvaro; Rincón,Oladis T; Rodríguez,Raquel; Romero,Nathalie; Rincón,Ana Ismenia;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2004,
Abstract: in this research a one-year study was run, for two different periods, in eight test stations of the zulian region, in which the corrosion rate of steel sae1010 and 99% copper were evaluated by weight loss. samples of 10×15cm were exposed to the prevailing wind direction in the natural environments, on racks with 45o inclination. deposition rates of chloride ions, sulfur dioxide, atmospheric dust, and the meteorological variables with greater incidence were determined. the planetario was the most aggressive station for the steel, with 26.10 μm/year, and the t. bachaquero test site for copper with 8.96 μm/year. in the repetition study for the first year of exposure, a comparative decrease from c5 to c4 was found, which was due to the faster formation of the protector patina as a result of the increment in contaminants deposition. later, the zulian maps of atmospheric corrosion for steel and copper were constructed, using pies to report the results, where the diameter of the pie represents the corrosion rate of the material in each zone and the size of the pie portions represent the effect of each variable in the atmospheric corrosion process.
Effect of pore sealer in the behavior of thermal sprayed aluminum and zinc coatings in marine and coastal marine atmospheres
Salas,Orlando; Rincón,álvaro; Rincón,Oladis T.; Sánchez,Miguel; Maldonado,Luis;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2006,
Abstract: the objective of this research is to study the effect that have pore sealers in the behavior of thermal sprayed cinc y aluminum, and zn/al coatings in marine and coastal marine atmospheres, during one year of exposition. to that effect, carbon steel sheets (10cm x 15cm × 3 mm) were sprayed by using two different processes (electric arch and flame spray), with and without the application of two additional layers of sealer. three sealers were evaluated: two wash primers of different suppliers, and a phenolic sealer. the sheets were exposed in two atmospheric test sites, la voz (coastal marine atmosphere), and the towers of the crossing of the lake of maracaibo (marine atmosphere). the sheets were characterized by means of initial weight, thickness, metallographic, adhesion, roughness, being evaluated monthly by visual inspection and photographic. the results showed that in these aggressive atmospheres, where the wind effect is important, the thermal sprayed zn/al coating, offers an excellent behavior even without sealer, producing galvanic protection to the substrate. in the case of thermal sprayed of cinc and aluminum coatings, a phenolic based pore sealer should be used, for covering completely the irregularities owned by this type of coating.
Evaluación de sistemas de recubrimientos duplex en ambientes marinos tropicales Evaluation of duplex coating’s system in tropical marine environments
Nathalie Romero,Oladis de Rincón,Miguel Sánchez,álvaro Rincón
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: En este trabajo se seleccionaron nueve esquemas de diferentes empresas del mercado nacional, de reconocida trayectoria, para realizar la evaluación en ambientes muy severos, marinos tropicales. A tal efecto se utilizaron perfiles de acero galvanizado nuevo y ya expuesto (con corrosión del sustrato), a las mismas condiciones de evaluación. Se seleccionaron dos estaciones de campo: La Voz y El Cruce del Lago de Maracaibo, ambos climas marinos tropicales de elevada agresividad. Adicionalmente, se efectuaron ensayos acelerados en una estación en el Centro de Estudios de Corrosión (CEC), utilizando la norma ISO 11474, y en el laboratorio (Cámara climática/PROHESION). Cabe destacar que luego de mas de 36 meses de exposición en las estaciones de campo, el desempe o de los diferentes esquemas sobre galvanizado ya expuesto se observa claramente definido, pudiendo seleccionar fácilmente el que muestra un mejor comportamiento. No obstante, para el caso del galvanizado nuevo, luego de este tiempo de evaluación, no se aprecia tan evidente la diferencia en el comportamiento; ya que esquemas de recubrimiento con un pobre desempe o en el galvanizado expuesto presentan un buen comportamiento en ese sustrato, demostrando la eficiencia de los sistemas Duplex. In this work nine different coating systems, from national suppliers, were selected to perform the evaluation in two severe tropical marine environments. New galvanized profiles as well as pre-exposed to the same environmental conditions were used as the test probes. Two different field stations were selected: La Voz and The Cross of Maracaibo Lake. Additionally, accelerated test were carried out in a station located at Centro de Estudios de Corrosión (CEC) by using the standard ISO 11474, and in the laboratory (PROHESION chamber). It is important to emphasize that after more than 36 month-exposure the behavior of the different coating systems on pre-exposed galvanized was clear, permitting to select the coating system with the best performance. Nevertheless in the case of new galvanized probes, after the evaluation period, most of the duplex systems had a very good performance.
Costos por corrosión en el mantenimiento preventivo y correctivo de equipos e instalaciones en la industria Corrosion costs in preventive and corrective maintenance in equipment and facilities in industry
Bertila Aponte,Matilde Fernández de Romero,Oladis oconis de Rincón,Silagdy Arias
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2008,
Abstract: El propósito de esta investigación fue determinar los costos por corrosión en función del tipo de corrosión y el control aplicado, asociados al mantenimiento correctivo y preventivo en una industria eléctrica y de alimentos en Venezuela, mediante la aplicación del “Software” SACIC dise ado para ello. Inicialmente, se hizo la clasificación de las órdenes de trabajo asociadas a las labores de mantenimiento para determinar las relacionadas con corrosión, durante un a o de operación de las plantas. Se seleccionaron 224 órdenes de trabajo en la industria eléctrica y 335 en la de alimentos. Según el tipo de corrosión la planta eléctrica tuvo un costo de 366.229.194,58 bolívares; de este total, los costos ocasionados por la corrosión uniforme y corrosión erosión fueron los más relevantes, mientras que para la planta de alimentos los costos fueron de 521.612.453 bolívares, generados en su mayor parte por corrosión uniforme. En lo que respecta a los costos generados por control de corrosión, los mismos fueron de 527.105.626,76 bolívares para la planta eléctrica y de 742.766.105 bolívares para la planta de alimentos, representando el 10% y 5% del costo anual por mantenimiento respectivamente. Con este trabajo se logró, además de la segregación de los costos por corrosión y su impacto en los costos por mantenimiento, estandarizar un procedimiento para la determinación del costo en función del tipo y control de corrosión, aplicable a cualquier industria. The purpose of this research was to determine corrosion costs according to the corrosion types and the controls applied associated to corrective and preventive maintenance in an electricity plant and a processing food in Venezuela, through the Software SACIC designed for this application. Initially, it was done the classification of work orders associated with maintenance work to determine those related to corrosion, for one year of operation of the plant. There were chosen 224 working orders which corresponded to the electrical plant industry and 335 to the food industry. According to the type of corrosion, the electricity plant had a cost of 366,229,194.58 Bolivares, being the costs related to uniform and erosion corrosion the most relevant, while for the food processing plant the costs were 521,612,453 Bolivares, generated by uniform corrosion. In relation to the costs generated by corrosion control, they were 527.105.626,76 Bolivares in the electricity plant and 742.766.105 Bolivares in the food processing plant, which represented 10% and 5% of the annual maintaining cost, respectively. This research permitted
Development of a model to predict the durability of reinforced concrete structures in marine environment
Morón,Oleyda; de Rincón,Oladis; García,Cézar; Arrieta,Idelfonso; Bravo,José;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2003,
Abstract: this paper proposes a model that enable to estimate the durability of reinforced concrete structures exposed to marine environment. to that effect, different models proposed by the literature were used, where the diffusion coefficient is function of the concentration, departing of the fact that the transfer process of the chloride ions is controlled by purely diffusion flow. a total of 44 concrete nucleus served as base for this research. thus, the results of chloride ions contamination determined in different elements of the general rafael urdaneta bridge (pgru) were used. the pgru, a 39 year structure, is located front caribbean sea with a very aggresive environmental condition. the results indicate that it does not exist an unique model that is applied to all the evaluated structure, for the valuation criteria assumed in the selection of the models, but, as a rule depend on the quality of the concrete (equal model for a same element). however, the hall′s model was the one which fit better to the results (70% of the cases).
Operational factors affecting the hot dip galvanizing steel
Sánchez,Miguel; Contreras,Ramón; Pérez,Orlando; de Rincón,Oladis; Campos,William;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: an evaluation by hot dip galvanizing on steel after a 1; 2 and 3-minutes immersion was studied. these samples were carried out for evaluating microhardness and thickness measurements. electrochemical techniques were used to determined the corrosion rate of steel in acid pickling 5; 10 and 16% hcl; rinsed with water of ph 2.50; 3.50 and 4.50 and hot dip galvanized steel in 3.5% nacl. certain operational parameters were analyzed, such as the aging bath (hcl), and elimination of the rinsing stage, to observe their influence in the hot dip galvanizing coating. it was found that an increase of coating thickness of hot dip galvanizing steel decreased the corrosion rate and the microhardness. surfaces of alloy layer of the coating were examined by scanning electron microscope (sem). sem measurements was determined that when obvious the rinsing, the chlorine can be catched between two layers (interface), and soon migrates of the outermost alloy layer of the coating (delta) towards the innermost one (gamma).
Factores operacionales que afectan el comportamiento del acero galvanizado por inmersión en caliente Operational factors affecting the hot dip galvanizing steel
Miguel Sánchez,Ramón Contreras,Orlando Pérez,Oladis de Rincón
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2007,
Abstract: En este trabajo se presentan los resultados de la evaluación de probetas de acero galvanizado por inmersión en caliente con tiempo de ba o de 1, 2 y 3 minutos. Se realizaron ensayos de espesor de recubrimiento y mediante técnicas electroquímicas se midió la velocidad de corrosión del acero en soluciones de ba os ácidos a 5; 10 y 16% de HCl y agua de enjuage pH 2,50; 3,50 y 4,50; y del acero galvanizado en una solución de NaCl 3,5%. Se analizaron ciertos parámetros operacionales, tales como el envejecimiento del ba o ácido (HCl), y eliminación de la etapa de enjuague, para observar su influencia en el recubrimiento de cinc. Se encontró que a medida que aumenta el espesor del recubrimiento disminuye la velocidad de corrosión. Mediante el uso del microscopio electrónico de barrido se determinó que cuando se obvia el enjuague, el cloro puede quedar atrapado entre dos capas (interfase), y luego migra de la capa superior (Delta) hacia la inferior (Gamma). An evaluation by hot dip galvanizing on steel after a 1; 2 and 3-minutes immersion was studied. These samples were carried out for evaluating microhardness and thickness measurements. Electrochemical techniques were used to determined the corrosion rate of steel in acid pickling 5; 10 and 16% HCl; rinsed with water of pH 2.50; 3.50 and 4.50 and hot dip galvanized steel in 3.5% NaCl. Certain operational parameters were analyzed, such as the aging bath (HCl), and elimination of the rinsing stage, to observe their influence in the hot dip galvanizing coating. It was found that an increase of coating thickness of hot dip galvanizing steel decreased the corrosion rate and the microhardness. Surfaces of alloy layer of the coating were examined by scanning electron microscope (SEM). SEM measurements was determined that when obvious the rinsing, the chlorine can be catched between two layers (interface), and soon migrates of the outermost alloy layer of the coating (Delta) towards the innermost one (Gamma).
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