Mo Effect on Natural Passivation and Corrosion Behavior of Duplex Stainless Steels in Alkaline Media

The role of Mo in the natural passivation behavior and pitting corrosion resistance of duplex stainless steels (DSSs) in alkaline medium was investigated by X-ray photoelectron spectroscopy and electrochemical analyses as a function of immersion time. It is shown that the Mo participated directly in the formation process of natural passive film, which affected the chemical distribution and thickness of the film by modifying the contents of other species (e.g. Cr oxide). With the increasing of prepassivation time, the oxidized Cr species were gradually enriched in the passive film, and the corrosion resistance of DSSs in alkaline solution containing Cl − was enhanced. Mo greatly improved the pitting corrosion resistance and the tolerance to Cl − attack of the passive film formed on DSS surface by inhibiting the initiation and growth of pitting.