Corrosion Resistance and Semiconducting Properties of the Passive Films on Duplex Stainless Steel 2205

In this study, the effect of molybdate on the electrochemical behavior and semiconductive properties of duplex stainless steel 2205 passive film at NaCl solutions was investigated. Cyclic potentiodynamic polarization, impedance spectroscopy, mottschottky plots and scanning electron microscopy (SEM) were used to study the passive behavior. Polarization curves showed that the corrosion current and passive current density of stainless steel decreased with increasing molybdate concentrations. Mott–Schottky analysis revealed that the passive films formed on duplex stainless steels behave as ntype and ptype semiconductors and the donor and acceptor densities reduced with increasing molybdate concentration. Electrochemical impedance spectroscopy (EIS) results showed that charge transfer and passive resistance increased in the presence of molybdate. In addition, double layer and film capacitance decreased with increasing molybdate concentration and passive film thickness increased. Scanning electron microscopy was used to study the steel surface and showed more uniform surface with lower damage in the presence of molybdate.