comparative study of the electrochemical behaviour of iron in alkaline media containing red mud and grey slurries. the effect of Al3+

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 slurried shows that Al3+ is the main common element. Therefore, 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. The electrochemical study using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) together with surface analysis techniques allowed to conclude that Al3+ blocks the surface of steel in alkaline media chloride increasing the steel resistance to chlorides attack. (Author) 15 refs