ELECTROCHEMICAL AND MOSSBAUER-SPECTROSCOPY STUDIES OF THE CORROSION OF IRON IN A MEDIUM MODELING ACID-RAIN

The passivation of low carbon steel was studied in aqueous solutions o f 0.5 M Na2SO4 + 0.001 M NaHSO3 (pH 3.5, 6.5 and 8.5) which can be con sidered as a model of acid rain [1]. Electrochemical and conversion el ectron Mossbauer spectroscopy (CEMS) investigations proved that the su lfite ions induce pitting corrosion at pH 3.5 and 6.5, while the measu rements showed suppressed pitting at pH 8.5. Only gamma-FeOOH was foun d as a corrosion product at pH 6.5 and 8.5, nevertheless, at pH 3.5 th e Mossbauer lines belonging to Fe3C appear in the spectra, and also Fe SO4 . H2O was detected after the shortest polarization time.