Publication: Corrosión de aleaciones ligeras. Procesado por vía semi-sólida, adición de Nd y tratamientos de anodizado avanzados
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2017-05-23
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Universidad Complutense de Madrid
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Abstract
La política medioambiental de la Unión Europea ha impuesto una serie de restricciones que afectan de forma directa a la industria del transporte. Así por ejemplo en automoción, ha limitado la cantidad de emisiones de gases de combustión en vehículos ligeros de pasajeros (95 g CO2/km para el 2020). Además ha establecido un listado de compuestos químicos potencialmente dañinos para la salud y medioambiente que deben ser retirados antes de 2018. Entre ellos se encuentran el ácido crómico, componente básico de los electrolitos empleados en el anodizado de aleaciones de aluminio en la industria aeronáutica. Estas limitaciones presentan un gran desafío para la industria del transporte, ya que debe ser capaz de encontrar nuevos materiales y tratamientos superficiales alternativos a los procesos actuales con el fin de alcanzar los requerimientos exigidos en un plazo relativamente corto de tiempo. Dada la relación directa que existe entre el consumo y la masa del vehículo, no es de extrañar que una de las medidas tomadas por los principales fabricantes de automóviles sea la sustitución de materiales tradicionales, como el acero, por otros más ligeros. El aluminio y el magnesio son los más ligeros de los metales estructurales. Esto, unido a las excelentes propiedades que presentan sus aleaciones y a su buena reciclabilidad, los sitúa como candidatos excepcionales para su empleo en automoción y, en general, en la industria del transporte. Desde el punto de vista de la resistencia a la corrosión, las propiedades del aluminio puro son excelentes, sin embargo la incorporación de elementos aleantes necesarios para mejorar el comportamiento mecánico pueden reducir considerablemente su resistencia a la corrosión debido, entre otras razones, a la formación fases secundarias de diferente naturaleza electroquímica. El magnesio puro y sus aleaciones presentan una elevada susceptibilidad a la corrosión en medios agresivos debido a su propia naturaleza activa y su poca tendencia a la formación de películas pasivas de carácter protector. Por tanto, es habitual recurrir al empleo de tratamientos superficiales cuando se pretende garantizar una duradera vida en servicio de las aleaciones comerciales de aluminio y magnesio...
The European Union environmental policy has resulted in a number of restrictions that directly affect the transport industry. For instance, in the automotive industry, the total emissions of combustion gases from passenger vehicles have been limited to 95 g CO2/km by 2020. Additionally, a list of potentially dangerous chemicals that must be removed from the market before 2018 has been established. Chromic acid, which is the main component of electrolytes used for anodising in aircraft, has been included in this list. These limitations are a great challenge for the transport industry since new materials and alternative surface treatments should be developed in order to meet the requirements in a relatively short period of time. Since weight and fuel consumption are directly related, vehicle manufacturers have chosen to replace traditional materials such as steel, for lighter ones. Aluminium and magnesium are the lightest among the structural materials, have excellent properties and are easily recycled. These advantages make them particularly interesting for the transport industry. From the corrosion point of view, aluminium behaviour is outstanding; however the addition of alloying elements for improving its mechanical properties may reduce its corrosion resistance due to the formation of electrochemically active secondary phases, among other factors. Magnesium and its alloys are highly susceptible to corrosion in aggressive environments due to their active nature and to its low tendency to form passive layers. Thus, surface treatments are a common practice in those applications where it is intended to maximize the working life of the material...
The European Union environmental policy has resulted in a number of restrictions that directly affect the transport industry. For instance, in the automotive industry, the total emissions of combustion gases from passenger vehicles have been limited to 95 g CO2/km by 2020. Additionally, a list of potentially dangerous chemicals that must be removed from the market before 2018 has been established. Chromic acid, which is the main component of electrolytes used for anodising in aircraft, has been included in this list. These limitations are a great challenge for the transport industry since new materials and alternative surface treatments should be developed in order to meet the requirements in a relatively short period of time. Since weight and fuel consumption are directly related, vehicle manufacturers have chosen to replace traditional materials such as steel, for lighter ones. Aluminium and magnesium are the lightest among the structural materials, have excellent properties and are easily recycled. These advantages make them particularly interesting for the transport industry. From the corrosion point of view, aluminium behaviour is outstanding; however the addition of alloying elements for improving its mechanical properties may reduce its corrosion resistance due to the formation of electrochemically active secondary phases, among other factors. Magnesium and its alloys are highly susceptible to corrosion in aggressive environments due to their active nature and to its low tendency to form passive layers. Thus, surface treatments are a common practice in those applications where it is intended to maximize the working life of the material...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, leída el 25/05/2016. Tesis formato europeo (compendio de artículos)