Mössbauer studies of first-stage corrosion products on iron powder and corrosion products on highly corroded nails

Magnetic iron powders were treated in solutions containing NaCl or CH₃ COONa as corrosion agents at 298 K and the oxide layers produced on the iron surface were identified by means of Mössbauer spectrometry. The measurement of Mössbauer spectra at various temperatures was useful to assign the chemical species produced on the surface. The spectra consisted of the superparamagnetic doublet peaks of polymorphic forms of FeOOH at room temperature. Highly corroded nails collected from different environments, i.e. sea coast, volcanic hot spring and an inland house, were examined to characterize the atmospheric corrosion products of nails. As a result, it was found that a-FeOOH and γ-Fe₂O₃ were present in every case. β-FeOOH and Fe₃O₄ were detected in nails collected at sea coast, volcanic hot spring and an inland house, respectively. The above results show that chemical pollution in the atmosphere is reflected in the species of corrosion products of nails exposed. Long-time exposure of nails resulted in the formation of γ-Fe₂O₃ and a-FeOOH.