Mass gain during oxidation, texture and residual stresses in oxide layers on polycrystalline Armco iron substrates with different surface conditions are investigated using thermogravimetry microscopy and synchrotron X-rays. The mass gain during oxidation in all samples follows a parabolic law. The parabolic oxidation constant increases with increasing roughness of a mechanically ground respectively polished oxide layer. Electrolytic polishing (grain surface etching) reduces while grain boundary etching increases the parabolic oxidation constant compared to the mechanically polished sample. All oxide layers show columnar growth of the magnetite and a moderate fiber texture. The magnetite contains compressive residual stresses. Under the conditions chosen for the oxidation treatment the magnitude of these compressive residual stresses does not depend on the substrate surface condition.