Using Mossbauer spectroscopy of conversion and Auger electrons and X-ray photoelectron spectroscopy peculiarities and regularities in formation of composition and structure of the products of oxidation of 57Fe samples in solutions of 0.1 N NaOH, a mixture of 1 N NaOH and 6 N NaNO3, 1 N H2SO4, 0.1 N H3BO3, and 0.5 mol/L Na2B4O7 in relation to the nature of corrosion medium and charge densities of anode polarization (10…12000 mA/cm2) corresponding to the region of passive-transpassive transition has been studied.