Mossbauer spectroscopic study of rust formed on a weathering steel exposedfor 15 years in an industrial environment

The rust formed on weathering steel exposed to an industrial environment fo r 15 years was characterized by means of X-ray powder diffraction, Raman sp ectroscopy, electron probe microanalysis and Mossbauer spectroscopy. The ru st consists of the crystalline alpha -FeOOH, gamma -FeOOH and an X-ray amor phous phase. The amount of the X-ray amorphous phase exceeds 50% of the tot al amount of the rust. The Fe-57 Mossbauer spectra observed at 10 K indicat e that the rust contains only alpha -FeOOH and gamma -FeOOH. The X-ray amor phous phase in the rust layer, which gives no peak in the X-ray diffraction pattern, is mainly alpha -FeOOH which shows a paramagnetic doublet due to the superparamagnetism occurring for small particle sizes at room temperatu re. The particle size of alpha -FeOOH is widely distributed and the inner r ust layer contains relatively well-crystallized alpha -FeOOH compared to th e outer layer.