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>2S04 solutions was monitored at 20 °C up to 3 months and at 90 °C up to 3 days. All corrosion products were analyzed by X-ray diffraction and Fourier transform IR spectroscopy. Four oxide phases, lepidocrocite (y-FeOOH), goethite (a-FeOOH), magnetite (Fe3C>4) and hematite (a-Fe203), were found in the corrosion products. Their distribution or absence of some oxide phases in corrosion products were strongly dependent on the experimental conditions. The strong influence of (NH4>2S04 electrolyte on the phase composition of the rust was explained by the cumulative effect of two aggressive ions, NH4 and SO4. Possible pathways for the formation of iron oxide phases in the rust were discussed

FT-IR and Mossbauer Study of Corrosion of Steel in Tap and Mineral Water

The influence of carbonates on the process of corrosion of steel in aqueous media has been studied. The corrosion of steel in tap water and mineral water of three different chemical compositions (all for human use) was monitored for up to 6 months. Rust samples were analyzed using Fourier transform infrared (FT-IR) spectroscopy and 57 Fe Mossbauer spectroscopy. Some selected samples were also analyzed by X-ray powder diffraction (XRD).It was shown that the concentration of carbonates plays an important role in the corrosion of steel in aqueous media, both during short (days), and long times (months) of corrosion. For short times of corrosion in the presence of a high content of carbonates, the rust was found amorphous for XRD. It was proved that "\u27(-FeOOHwas absent in amorphous rust. The possible presence of ferrihydrite in this amorphous fraction is discussed taking into account the FT-IR and Mossbauer spectroscopic results. At a very high concentration of carbonates, after 6 month of corrosion,\u27(-FeOOHwas not found in the rust. Formation of a-FeOOH and Fe304 in corrosion products was also monitored. It was suggested that, in the very early stages of corrosion, carbonates can be structurally incorporated in the rust in the form of hydroxycarbonates, while in the later stages, they can modify the phase transformation by the mechanism of specific adsorption

Formation of Rust During the Corrosion of Steel in Water and (NH4)2SO4 Solutions. Part II

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2SO4 solutions at 20 °C for time periods up to 6 months were investigated by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mössbauer spectroscopy. Three oxide phases, y-FeOOH (lepidocrocite), Fe304 (magnetite) and a-FeOOH (goethite) were detected in the rust samples. The distribution of these phases in the rust was dependent on the time of corrosion and the concentration of (NH4)2SO4. 57Fe Mössbauer spectroscopy indicated the substoichiometric character of magnetite (Fe3_I04). Magnetite was not observed in the rust generated in 2M (NH4)2SO4 solution. Fourier transfrom IR spectroscopy was particularly useful in the detection of very small amounts of goethite and lepidocrocite in the rust. The strong influence of (NH4)2SO4 electrolyte on the corrosion of steel in aqueous medium was explained as a cumulative effect of two aggresive ions, NH4+ and SO42-

Formation of Rust During the Corrosion of Steel in Water and (NH4)2SO4 Solutions. Part II

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2SO4 solutions at 20 °C for time periods up to 6 months were investigated by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mössbauer spectroscopy. Three oxide phases, y-FeOOH (lepidocrocite), Fe304 (magnetite) and a-FeOOH (goethite) were detected in the rust samples. The distribution of these phases in the rust was dependent on the time of corrosion and the concentration of (NH4)2SO4. 57Fe Mössbauer spectroscopy indicated the substoichiometric character of magnetite (Fe3_I04). Magnetite was not observed in the rust generated in 2M (NH4)2SO4 solution. Fourier transfrom IR spectroscopy was particularly useful in the detection of very small amounts of goethite and lepidocrocite in the rust. The strong influence of (NH4)2SO4 electrolyte on the corrosion of steel in aqueous medium was explained as a cumulative effect of two aggresive ions, NH4+ and SO42-