Corrosion of steel in carbonated media: The oxidation processes of chukanovite (Fe2(OH)2CO3)

The oxidation of aqueous suspensions of chukanovite (Fe2(OH)2CO3) obtained by mixing NaOH, FeCl2 and Na2CO3 solutions was studied. The reaction was monitored by recording the pH and the redox potential of a platinum electrode immersed in the suspension. The precipitate was analyzed at various oxidation stages by infrared spectroscopy. The end products were also characterized by X-ray diffraction. The oxidation by air of the suspensions leads to lepidocrocite and goethite without formation of an intermediate green rust compound. Violent oxidation of chukanovite by hydrogen peroxide leads to a Fe(III) oxycarbonate with a crystal structure closely related to that of chukanovite.