FORMATION OF RUST DURING THE CORROSION OF STEEL IN WATER AND (NH4)2SO4 SOLUTIONS

Formation of rust during the corrosion of steel in water and (NH4)2SO4 solutions was monitored at 20-degrees-C up to 3 months and at 90-degr ees-C up to 3 days. All corrosion products were analyzed by X-ray diff raction and Fourier transform IR spectroscopy. Four oxide phases, lepi docrocite (gamma-FeOOH), goethite (alpha-FeOOH), magnetite (Fe3O4) and hematite (alpha-Fe2O3), were found in the corrosion products. Their d istribution or absence of some oxide phases in corrosion products were strongly dependent on the experimental conditions. The strong influen ce of (NH4)2SO4 electrolyte on the phase composition of the rust was e xplained by the cumulative effect of two aggressive ions, NH4+ and SO4 2-. Possible pathways for the formation of iron oxide phases in the ru st were discussed.