Effect of Thiosulfate on Corrosion Behavior and Passive Films of Duplex Stainless Steel 2205 in Chloride Solutions

Abstract

The effect of S2O32- 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 S2O32- decreased the pitting potential of duplex stainless steel 2205 in Cl--containing solutions. The corrosion resistance of passive films was influenced by the concentration of S2O32- 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 S2O32- were detected. The primary components of the passive films on duplex stainless steel 2205 in a Cl--S2O32- solution were Cr-oxides and Fe-oxides or hydroxides with small amounts of Ni and Mo oxides.