Efecto de la microestructura y la concentración del ácido en la corrosión de aleaciones binarias Pb-Sn

Borrego Navejas, Rocío (2015) Efecto de la microestructura y la concentración del ácido en la corrosión de aleaciones binarias Pb-Sn. Maestría thesis, Universidad Autónoma de Nuevo León.

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Resumen

Lead is a rare element in earth’s crust, but since it is found in concentrated deposits it can be produced at low cost, and ranks fifth in tonnage consumed after iron, copper, aluminum and zinc. Some of the many applications of lead are: automobile batteries, uninterruptible power sources, radiation shields in nuclear facilities or medical x-ray apparatus, etc. For the automobile batteries the common lead alloys are lead-antimony (Pb-Sb), lead-calcium-tin (Pb-Ca-Sn), lead-cadmium-antimony (Pb-Cd-Sb), or lead-tin (Pb-Sn). The Pb-Sn system is the most commonly used for valve regulated lead-acid batteries, which will be the object of study in the current work, which unlike previous works (1; 2) tin content is in a lower % range. The present work is aimed to study the behavior of Pb-Sn alloys treated under defined conditions of temperature and time as thermal treatments for the study of microstructure and corrosion effects. Once different thermal treatments were applied, its mechanical properties, micro-hardness, microstructure and corrosion rate were evaluated to determine which conditions generate the best performance. The temperatures used for thermal treatment were 175 and 250 °C with three different cooling temperatures 0, 25 and 50 °C. Once microstructures were evaluated, five samples of each thermal treatment were submitted to measure mechanical properties and another sample was used to determine microhardness. Then, another sample of each thermal treatment was used to evaluate electrochemical properties. Samples of the thermal treatments were tested by electrochemical attack at two different sulphuric acid concentrations to evaluate their corrosion rate.

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