Abstract
Red mud (RM) is the main by-product of the Bayer process for alumina extraction from bauxite, and grey slurries (GS) are generated during the granite rocks transformation processes. The huge volume of those wastes generated every year suppose a serious environmental problem. Recent works by our group demonstrate the efficiency of both types of muds as corrosion inhibitors for iron and steel in alkaline media containing chlorides. The elemental analysis of these slurries shows that Al 3+ is the main common element. Therefore, the aim of this paper is to study the effect of the soluble Al 3+ in the electrochemical behaviour of iron in alkaline media, in presence and absence of chlorides. The electrochemical study using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) together with surface analysis techniques allowed to conclude that Al 3+ blocks the surface of steel in alkaline media chloride increasing the steel resistance to chloride attack.
Highlights
Comparative study of the electrochemical behaviour of iron in alkaline media containing red mud and grey slurries
Recent works by our group demonstrate the efficiency of both types of muds as corrosion inhibitors for iron and steel in alkaline media containing chlorides
The aim of this paper is to study the effect of the soluble Al3+ in the electrochemical behaviour of iron in alkaline media, in presence and absence of chlorides
Summary
Los lodos rojos (LR) y los lodos grises (LG) son los principales residuos resultantes de dos procesos industriales ampliamente extendidos: mientras los primeros, LR, se originan en la extracción de la alúmina a partir de la bauxita, los segundos, LG, se generan durante los procesos de transformación del granito (corte y pulido de la piedra) en los que se produce un intenso desgaste de la roca, convirtiéndose en polvo alrededor de un 30 % de la misma. La figura 1 muestra el aspecto que presentan ambos tipos de lodos. Debido a las grandes cantidades de ambos lodos que se generan (470.000 y 30.000 T/ año, respectivamente, para LR y LG, sólo en Galicia) y su fuerte alcalinidad (pH ≈ 12.0), representan un importante problema medioambiental en las áreas donde están implantadas las industrias y en las zonas donde se acumulan[1 y 2]. Ese problema medioambiental ha hecho que se hayan dedicado una importante cantidad de esfuerzos al estudio de aplicaciones para poner en valor estos residuos y darles así una salida[3,4,5]. Ambos tipos de lodos como inhibidores de la corrosión del hierro y acero en disoluciones alcalinas cloruradas. El objetivo de este trabajo es analizar el efecto de uno de los elementos de composición mayoritario y común a ambos tipos de lodos: los iones aluminato
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