Publication: Simulación mediante circuitos equivalentes de la impedancia electroquímica de armaduras de acero inoxidable en mortero
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2014-03
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2014-03-12
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Abstract
El presente proyecto aborda la tarea de simular el comportamiento frente a la corrosión de refuerzos de acero inoxidable corrugados embebidos en mortero, cuando el conjunto está expuesto a ciertos medios agresivos durante un periodo de tiempo de 8 años. El interés de este estudio radica en la novedad de simular el comportamiento de impedancias electroquímicas de los refuerzos a largo plazo. Por ello, los resultados arrojados pueden ser útiles en el ámbito de las estructuras para edificación. Diversos grados de aceros inoxidables constituyen las armaduras que se han estudiado: un acero inoxidable austenítico bajo en níquel AISI 204 Cu, un austenítico tradicional 304, los austeníticos AISI 316L y 316 Ti, un inoxidable dúplex AISI 2205. Por último, se ha tomado, a modo de referencia un acero al carbono tradicional. Las armaduras están constituidas por barras corrugadas, y éstas son de dos clases: barras de un solo material, y barras unidas mediante soldaduras. A su vez, de las segundas se exponen en dos grupos. Por un lado, se tiene cada material soldado frente a sí mismo, y por otro, los mismos materiales soldados frente al acero al carbono. Las condiciones a las que se expusieron las probetas constituidas por refuerzos embebidos en mortero son dos: Inmersión en agua con un contenido del 3,5% de cloruro sódico, y exposición a un ambiente de elevada Humedad Relativa (HR), en torno al 95%, con adición de cloruros en el mortero. En este proyecto, desde el comienzo se parte de unos datos de impedancia experimentales ya existentes, correspondientes a las probetas que se han descrito. Estos datos fueron adquiridos mediante ensayos de Espectroscopia de Impedancia Electroquímica (EIS) por un equipo de investigación del Departamento de Ciencia de Materiales e Ingeniería Química de la Universidad Carlos III de Madrid. Para realizar las simulaciones, se ha empleado un software especializado (Zview). Lo que se busca es obtener un ajuste gráfico de los datos experimentales. Para ello, a partir de las herramientas que ofrece el programa, se deben diseñar y aplicar modelos de circuitos equivalentes que reproduzcan una respuesta de impedancia lo más aproximada posible a los datos de ensayos EIS. Sin embargo, cualquier circuito no sirve, es necesario además, que los modelos de circuito estén diseñados con elementos que expliquen los procesos reales que se van a simular. El trabajo realizado a lo largo de la investigación en este proyecto ha permitido concluir que los tres circuitos equivalentes, planteados y empleados en la simulación de impedancias, proporcionan una buena aproximación de los sistemas reales. Además, la obtención de información cuantitativa de sus parámetros ha permitido relacionar los diferentes procesos que constituyen el comportamiento frente a la corrosión de los materiales.
The aim of this project is to simulate, through equivalent circuit models, the corrosion behaviour of stainless steel reinforcements embedded in concrete, under different aggressive environments after 8 years of exposure. The results showed in this work could be interesting for structural edification scopes. According the several reinforcements studied, there are different stainless steels: low nickel austenitic stainless steel AISI 204Cu, a traditional austenitic AISI 304, austenitic steels AISI 316L and 316Ti, and the duplex stainless steel AISI 2205. Moreover, traditional carbon steel has been included as reference. There are two groups of corrugated reinforcements: rebars composed of single steel, and welded rebars made of two materials. This second group of welded bars are divided in two subgroups. Firstly, there are bars welded of a single material, and secondly, each single material welded with carbon steel. There are two environments of exposure: partial immersion in 3.5% NaCl solution, and chloride addition to the mortar and exposure to high relative humidity (95%). This project used, as starting point, the experimental impedance data relating to the reinforcements in mortar samples. This data were collected through Electrochemical Impedance Spectroscopy tests (EIS) by a research team working for Materials Science and Chemical Engineering Department in Carlos III University of Madrid. To simulate impedances, specialised software has been used: Zview by Scribner Associates. The goal of its application is the fitting of experimental impedance data. For this purpose, the software provides several tools, which allows the user to design and apply equivalent circuits for the impedance fitting. Therefore, the impedance response provided by the circuit models must simulate the experimental data accurately. However, this is not the only requirement the circuits need to meet, but also, they must identify the real processes which are taking place. The study carried out in this project draws a number of conclusions on the equivalent circuits applied for the impedance modelling. Firstly, these circuits provided a good approach for the systems studied. Moreover, the parameter values of these models can explain the different processes involved in the corrosion behaviour of the materials.
The aim of this project is to simulate, through equivalent circuit models, the corrosion behaviour of stainless steel reinforcements embedded in concrete, under different aggressive environments after 8 years of exposure. The results showed in this work could be interesting for structural edification scopes. According the several reinforcements studied, there are different stainless steels: low nickel austenitic stainless steel AISI 204Cu, a traditional austenitic AISI 304, austenitic steels AISI 316L and 316Ti, and the duplex stainless steel AISI 2205. Moreover, traditional carbon steel has been included as reference. There are two groups of corrugated reinforcements: rebars composed of single steel, and welded rebars made of two materials. This second group of welded bars are divided in two subgroups. Firstly, there are bars welded of a single material, and secondly, each single material welded with carbon steel. There are two environments of exposure: partial immersion in 3.5% NaCl solution, and chloride addition to the mortar and exposure to high relative humidity (95%). This project used, as starting point, the experimental impedance data relating to the reinforcements in mortar samples. This data were collected through Electrochemical Impedance Spectroscopy tests (EIS) by a research team working for Materials Science and Chemical Engineering Department in Carlos III University of Madrid. To simulate impedances, specialised software has been used: Zview by Scribner Associates. The goal of its application is the fitting of experimental impedance data. For this purpose, the software provides several tools, which allows the user to design and apply equivalent circuits for the impedance fitting. Therefore, the impedance response provided by the circuit models must simulate the experimental data accurately. However, this is not the only requirement the circuits need to meet, but also, they must identify the real processes which are taking place. The study carried out in this project draws a number of conclusions on the equivalent circuits applied for the impedance modelling. Firstly, these circuits provided a good approach for the systems studied. Moreover, the parameter values of these models can explain the different processes involved in the corrosion behaviour of the materials.
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Keywords
Acero, Ensayo de materiales, Electroquímica