Initial oxidation of Fe-Al and Fe-Cr-Al alloys: Cr as an alumina booster

The boosting effect of Cr on the growth of the protective alumina scale on Fe-Al alloys is investigated by x-ray photoelectron spectroscopy. Using low oxygen pressure the surface chemistry of the alloys is monitored starting from the first moments of oxidation. Chromium effect on the Fe-Al surface-bulk exchange is clearly detected by analyzing the measured surface concentrations within the atomic concentration models. Previous ab initio calculations agree well with the present experiments.