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