Surface analytical investigation of the electrochemical and corrosion behaviour of nanocrystalline FeAl8

From the higher fraction of grain boundaries in nanocrystalline substances a different corrosion behaviour in comparison to the conventional polycryst alline material can be expected, which may be utilised for the development of new corrosion resistant alloys. Therefore, the oxidation behaviour of th ese two different crystallisation states of FeA18 was compared by means of electrochemical and surface analytical experiments. The oxide films formed after electrochemical passivation were investigated by Auger Electron Spect roscopy. The application of inelastic peak shape analysis by the method of Tougaard showed, that for both materials the oxide layer may be described b y a model of a (below the contamination) buried layer with a thickness of o nly a few nanometers depending on the preparation conditions. Factor Analys is was applied for the evaluation of the differentiated low energy Auger el ectron spectra (20-100 eV) as a function of depth profiling sputtering time . For both, the nanocrystalline and the polycrystalline material, the inner part of the oxide layer was enriched in Al, whereas the very outer part (s urface region) was enriched in Fe. No differences concerning the sputtering time for removal of the oxide layers were found for the two alloys.