RESUMENLas baterías de automóviles no solo son afectadas por el uso y desgaste, sino también por otros factores como la concentración del electrolito, la pérdida de agua y la temperatura a la que puede estar expuestas, siendo este último el factor de mayor influencia permitiendo así un incremento en la velocidad de corrosión en las aleaciones de plomo (componentes de la batería) afectando a su vez el tiempo de servicio. Por consiguiente, para la industria de las baterías de automóviles tipo plomo-ácido, es muy importante estudiar el efecto de la temperatura en el funcionamiento de las placas negativa y positiva, durante el proceso de carga y descarga que se llevan a cabo en las baterías durante su vida útil, y además, al estar expuesta a un electrolito de ácido sulfúrico.De acuerdo a lo anterior, en este trabajo de grado se estudió la influencia de la temperatura en la velocidad de corrosión sobre la aleación plomo-antimonio, a través de las técnicas electroquímicas: espectroscopia de impedancia electroquímica (EIS), extrapolación de Tafel, curva potenciodinámica y voltametría cíclica. Las pruebas se realizaron a uno y cinco días de exposición en ácido sulfúrico 0.5 M, a temperaturas de 25 y 65°C en una celda plana con intercambiadores de calor para controlar la temperatura en el equipo GAMRY 600. Los potenciales fueron medidos respecto al electrodo de referencia de calomel saturado, y se utilizó como electrodo auxiliar una barra de grafito. Por último, se realizó un análisis de los productos de corrosión formados por medio de microscopía electrónica de barrido (SEM).Palabras clave: Baterías Tipo Plomo-ácido, Velocidad de Corrosión, Temperatura, técnicas electroquímicas. ABSTRACTCar batteries are not only affected by their use and wear but also by other factors such as electrolyte concentration, water loss and temperature that can be exposed, the latter being the most influential factor causing an increase in the corrosion rate of lead alloys (battery components), and affecting their service time. Therefore, for the industry of automobile batteries lead-acid type is very important to study the effect of temperature on the functioning of positive and negative grids during charging and discharging, which are carried out in batteries lifetime to be exposed to the sulfuric acid electrolyte.According to all of the above described, in this research work the influence of temperature in the corrosion rate of lead-antimony alloy was studied by electrochemical techniques: Electrochemical impedance spectroscopy (EIS), Tafel extrapolation, curve potentiodynamic and cyclic voltammetry. The tests were performed for exposure times of one and five days at temperatures of 25 and 65°C in sulfuric acid 0.5 M in flat cell with heat exchangers to control the temperature in the machine GAMRY 600. The potentials were measured regard to the calomel saturated reference electrode and a graphite bar was need as auxiliary electrode. Finally, the corrosion products formed were examined by a test of scanning electron microscopy (SEM).
Fatigue cracking in metallic materials occurs mainly due to the effect of cyclic stresses and their variation of magnitude over time. To evaluate the fatigue strength based on S-N curves, many tests are needed, which require a lot of time and incur high costs. For this research, several tests were conducted on examples of high-strength steel to determine their mechanical properties, chemical composition and fatigue. It was found that (Charpy V Notch) CVN impact toughness, the percentage of alloying elements and the mechanical properties of the tension test show a positive lineal effect in relation to the fatigue strength of the materials evaluated. Finally, a correlation was found that showed a very good fit between the experimental fatigue data and the predicted values. The correlation, based on Charpy impact energy tests, the relation to the yield stress, the ultimate stress, and the hardness of the material, allows one to predict resistance to fatigue at a low cost.
A model is presented to evaluate the effect of the roughness and the profile of concentration of hydrogen in a low carbon steel. The model takes advantage of the Pick's Second Law, to predict the transport of hydrogen in the steel. The problem is treated as a variational one and its space solution is made numerically by means of the Finite Elements Method, while the temporal equation is solved via the Finite Differences Method, in order to determine the concentration profiles c: »f Hydrogen in the steel and to quantify the roughness effect. Simultaneously, bipotentiostatic hydrogen permeation test were performed to evaluate the coefficient of mass transfer.
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