Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
J. Phys. IV France 03 (1993) C9-133-C9-141
Investigation of the transient state of oxidation-chloridationE. Reese, E.M. Müller-Lorenz and H.J. Grabke
Max-Planck-Institut für Eisenforschung GmbH, Abteilung Physikalische Chemie, Max-Planck-Str. 1, 4000 Düsseldorf, Germany
The transient state of the simultaneous oxidation and chloridation of Fe-2.25Cr- 1Mo at 773 K and Fe-25Cr-2ONi-Nb at 973 K have been studied in He-O2-H2O-HCl and N2- H2-H2O-HCl mixtures in short term oxidation tests. The surface of the corroded samples were examined by SEM and AES. The simultaneous attack of O2 and Cl2 leads to the formation of metal oxides and chlorides side by side on the alloy surfaces during the early stage of reaction, although the chlorides are not in stable equilibrium with the gas phase. After longer exposure times only the thermodynamically stable oxides were detected in the outer scale, however, at the metal/oxide interface chloride layers are still present. The initial simultaneous growth of oxides and chlorides strongly affects the structure and morphology of the subsequently formed oxide scales.
© EDP Sciences 1993