On the formation of β-FeOOH (akaganeite) in chloride-containing environments

Fe(III) oxyhydroxides were synthesised in chlorinated environments via chemical or electrochemical processes in order to determine the conditions favouring the formation of akaganeite. Corrosion products were characterised using X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The first method produced Fe(III) oxyhydroxides from the aerial oxidation of iron(II) precipitates which were obtained by mixing FeCl2 (.) 4H(2)O and NaOH solutions. Depending on the initial amounts of Fe, Cl and OH, goethite, lepidocrocite or akaganeite were then obtained. When a large excess of dissolved FeCl2 was present, akaganeite was formed independently of the oxygen flow. In the second method, steel electrodes were left in baths containing chloride with [Cl-] = 2 mol L-1, using either FeCl2 (.) 4H(2)O or NaCl. Akaganeite was obtained exclusively in the FeCl2 solutions, confirming that to obtain the formation of this compound, both iron(II) and chloride concentrations must be important. (c) 2006 Elsevier Ltd. All rights reserved.