Influence of anions on the structure and morphology of steel rust particles prepared by aerial oxidation of acidic Fe(II) solutions

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In order to simulate the atmospheric corrosion of steel, artificial steel rust particles were synthesized by aerial oxidation of aqueous solutions containing FeCl_2, FeSO_4 and NaNO_3, and the structure and morphology of the obtained particles were characterized by XRD and TEM. Needle-like SO_4^<2-> containing Schwertmannite (Fe_8O_8(OH)_6(SO_4)) particles were mainly formed in FeCl_2－FeSO_4, FeSO_4－NaNO_3, FeCl_2－FeSO_4－NaNO_3 systems, and the crystallization and particle growth of this material were not influenced by added Cl^- and NO_3^-. The rod-shaped β-FeOOH particles were formed from in only FeCl_3-NaNO_3 system, though no marked change in crystallite and particle sizes of the β-FeOOH was recognized by adding NO_3^-. Accordingly, it can be suggested that the corrosive SO_X gas and air-borne chloride strongly affect the rust formation in atmospheric corrosion of the steels.