The analysis of rusts formed on mild steel in pulp bleaching section

Rusts obtained from mild steel, exposed to different stages of the bleach section in a paper mill in south India, have been analysed by Fe 57 transmission Mössbauer spectroscopy and X-ray diffraction. All rust samples exhibit superparamagnetism due to fine particles. Corrosion products identified mainly are Fe 3- x O 4 (‘χ’ varying from 0.06 to 0.16) and α-FeOOH (>85%) while γ-FeOOH appears as a minor phase. In one case, mild steel exposed to the chlorination washer shower pipe, the rust components are observed to be Fe 3- x O 4 and β-FeOOH. An attempt has been made to find a correlation among corrosivity of the environment, non-stoichiometery of Fe 3O 4 and α-FeOOH/Fe 3- x O 4 ratio.