Mössbauer spectroscopic study of rust formed on a weathering steel exposed for 15 years in an industrial environment

The rust formed on weathering steel exposed to an industrial environment for 15 years was characterized by means of X-ray powder diffraction, Raman spectroscopy, electron probe microanalysis and Mossbauer spectroscopy. The rust consists of the crystalline α-FeOOH, γ-FeOOH and an X-ray amorphous phase, The amount of the X-ray amorphous phase exceeds 50% of the total amount of the rust. The 57 Fe Mossbauer spectra observed at 10 K indicate that the rust contains only α-FeOOH and γ-FeOOH. The X-ray amorphous phase in the rust layer. which gives no peak in the X-ray diffraction pattern, is mainly α-FeOOH which shows a paramagnetic doublet due to the superparamagnetism occurring for small particle sizes at room temperature, The particle size of α-FeOOH is widely distributed and the inner rust layer contains relatively well-crystallized α-FeOOH compared to the outer layer.