Preparation and Characterization of Model Colloidal Corrosion Products

Abstract

Abstract Model colloidal corrosion products consisting of ferric hydrous oxides, cobalt oxide, and chromium hydroxide particles of well defined shape and uniform size have been prepared. These systems are used to elucidate the mechanism of formation of such materials from aqueous solutions, with special emphasis on the nature and the distribution of solute complexes which act as precursors to precipitation. The role of the anions on the composition and the morphology of the resulting metal hydrous oxide solids is stressed. The so prepared model systems are also used to study properties of the solids and their reactions which are of interest in corrosion of metals. In this work, the magnetic characteristics of iron (III) hydrous oxides as a function of their composition, as well as particle size and shape, are illustrated and discussed. Furthermore, the interactions of a ferric oxyhydroxide with EDTA, a chemical decontaminant for nuclear reactors, has been investigated. It was shown that the stability of these particles and their rate of dissolution is strictly related to the adsorption of this ligand material on the metal hydrous oxide. Finally, the adhesion of chromium hydroxide particles on steel and their removal has been followed as a function of solution conditions (pH, electrolyte presence). The better data could be explained in terms of the theory of the electrical double layer.