The effect of S 2 O 3 2− on the corrosion behavior and passive films of duplex stainless steel 2205 in a Cl − -containing environment was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, Mott-Schottky measurements and XPS composition analysis. The results show that the addition of S 2 O 3 2− decreased the pitting potential of duplex stainless steel 2205 in Cl − -containing solutions. The corrosion resistance of passive films was influenced by the

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... n of S 2 O 3 2− in Cl − -containing solutions, but the exhibited n-type and p-type semiconductor characteristics were not affected. The modified stability and the variation in donor and acceptor densities of the passive film with the concentration of S 2 O 3 2− were detected. The primary components of the passive films on duplex stainless steel 2205 in a Cl − -S 2 O 3 2− solution were Cr-oxides and Fe-oxides or hydroxides with small amounts of Ni and Mo oxides.