QUANTITATIVE AUGER ANALYSIS OF PASSIVE FILMS FORMED ON STAINLESS-STEELS

Depth profiling analysis of passive films grown on the surface of Fe-17Cr, Fe-13.5Cr-3.5Si and Fe-12Cr-5Al alloys (with or without Mo additions) in acidic and basic media has been performed by Auger electron spectroscopy (AES) and ion sputtering. Original depth concentration profiles for oxidized iron and chromium inside the passive film and unoxidized (metallic) components of the alloys were extracted using the sequential-layer-sputtering model with the assumption of a step-like interface between the passivated overlayers and the metallic substrate. A quantitative analysis requires an accurate adjustment of the sputter rate employed as a fitting parameter (related here with numerical values of inelastic free paths). In this way, some consistent relationships can be established between the absolute atomic depth distributions of elements constituting the passive films, its thickness and the electrochemical characterization of the alloy resistance with regard to pitting corrosion.