Investigation of passive films formed on the surface of alloy 690 in borate buffer solution

The passive film formed on the surface of the alloy 690 in borate buffer solution was studied by potentiodynamic curves and electrochemical impedance spectroscopy. With the increasing of the passivation potential, the corrosion resistance of the alloy 690 reduced. Moreover, the corrosion resistance of the passive film was the lowest in the vicinity of 0.6 VSCE. These results were supported by XPS and Mott-Schottky analyses. The corrosion resistance of the alloy 690 increased with the increasing of passivated potential in borate buffer solution with chloride ion. The chloride ion decreased corrosion resistance of the alloy 690 according to point defect model.