The alloys based on the Fe-Mn-Al system are good candidates to replace the conventional stainless steel, which are based on the ternary alloy Fe-Ni-Cr. The Fe-Mn-Al system offers the possibility to replace strategic elements as Ni and Cr by others lighter and cheaper as Mn and Al, in addition it has attractive mechanical and corrosion resistance properties [1, 2]. Fe-9Cr-Mo is an important material for super-heater tubes in a power industrial plant. The presence of Mo enhances creep strength above 600 o C while chromium helps in forming a chromium-rich scale which protects the steels from further oxidation [3]. The aim of this paper is to investigate the oxidation behavior of Fe-9Cr-Mo (FCR) in comparison with oxidation behavior of two Fe-Mn-Al-C-Cr-Mo-Si alloys with different molybdenum (Mo) content, named as Mo(0) to sample without Mo and Mo(1) to specimen with Mo. The experiments were carried out at 600, 700, 750 and 850 o C, each one during 72 hours in static air. The oxidation kinetics was measure as a function of time using a Thermogravimetry analyzer, TGA. X-ray diffraction (XRD), Energy Dispersive Spectrometry (EDS) and Integral Conversion Electron Mossbauer Spectroscopy (ICEMS) [4] were used to characterize the structure and composition of the oxide scale. The TGA results show that at all oxidation temperatures the sample FCR exhibit the lowest kinetic corrosion and the lowest weight gain, whereas Mo(0) the highest, showing an important effect of Mo addition in Fe-Mn-Al-C samples. The highest weight gain is presented at high temperature oxidation testing to all samples. The oxidation products found in the external part of scale by XRD and EDS measurements were principally manganese-iron oxides in Mo(0) and Mo(1) samples, and iron-chromium oxides in FCR samples. In the internal part Mn(Fe, Al) 2 O 4 and (Fe, Cr) 2 O 3 species were found, respectively. By ICEMS technique were found hematite, probably maghemite, α -Fe and a paramagnetic doublet in FCR samples, but the line width of sextets is