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Duplex stainless steel (DSS) presents economical and technological importance due to a combination of excellent mechanical and corrosion properties. In particular, DSS posses good pitting corrosion resistance in chloride solution. This steel, when submitted to temperatures in the range of 300 to 1000 °C, which can occur during welding processes, thermo-mechanical treatments, and service conditions, presents the formation of several phases. Aging at low temperatures (about 300-400 °C) causes a significant degradation in the mechanical properties and corrosion resistance, due to the formation of chromium-rich phases and adjacent regions depleted of chromium. In this work, we investigated the correlation of the pitting corrosion resistance with the passive film composition for 2205 DSS. The samples were solution treated and then aged at 400 °C for 7000 hours. The film was grown in 0.1 M sulphuric acid solution using a potentiostat. The passive film composition was analyzed by X-ray photoelectron spectroscopy (XPS). The pitting corrosion resistance was evaluated by potentiodynamic polarization measurements in 3.56% sodium chloride solution. XPS results indicated that the passive film was rich in Cr3+, with a cationic fraction of approximately of 0.6. It was observed a correlation between the Cr/Fe ratio and the pitting potential in NaCl solution. |