Simulating study of atmospheric corrosion of steels in a coastal industrial zone: Effect of SO_3^<2-> on the formation of β-FeOOH rust particles synthesized from FeCl_3 solutions

For simulation of the atmospheric corrosion of steel in a coastal industrial district, β-FeOOH rusts were synthesized by aging the aqueous FeCl_3 solutions containing SO_3^<2->. The yield and crystallite size of β-FeOOH were remarkably decreased by adding SO_3^<2->, implying the suppression of formation and crystallization of β-FeOOH. Before aging, added SO_3^<2-> broke the coordination of Cl^- and OH^- to Fe_<3+> in Fe^<3+>-complexes and reduced the Fe^<3+> to Fe^<2+>. These facts suppose that SO_3^<2-> generated by dissolution of SO_X gas in thin film water on the steels at a coastal industrial zone markedly inhibits the formation of β-FeOOH rust.