Chlorine-Induced High Temperature Corrosion: I. Metals and Alloys - a Review

Abstract

A review is presented on the available results of the corrosion of Co, Ni, Cr, Fe and their alloys in oxidizing and in oxidizing/sulphidizing atmospheres in the presence of chlorine. The thermodynamic aspect of the reactions between the metal and chlorine or hydrogen chloride are discussed using stability diagrams. The saturated vapour pressures of some chlorides are also reported.It was clear from the results on the high temperature corrosion of metals and alloys in oxidizing environments that small additions of hydrogen chloride or chlorine accelerate the (oxidation) corrosion reactions. A mechanism has been proposed describing this “active oxidation” by several reaction steps and transport phenomena. The “active oxidation” is based on two simultaneous processes: 1) solid state diffusion, and 2) vapour phase transport of metal species. In oxidizing/ sulphidizing environments, contradictory results have been obtained, but it is suggested that in this case, too, the corrosion is based on solid state diffusion and vapour phase transport of the metal species. © 1992, Walter de Gruyter. All rights reserved.