Electrochemical corrosion behaviors of 316L stainless steel used in PWR primary pipes

The effects of temperature and Cl^-and dissolved oxygen (DO) concentrations on the electrochemical corrosion behaviors of 316L stainless steel used in pressurized water reactor primary pipes were investigated via a composite design strategy, potentiodynamic polarization and electrochemical impedance spectroscopy measurements, and oxide film morphology observation. The results reveal that temperature is the most significant factor affecting the corrosion behavior of the steel:the higher the temperature, the higher the corrosion current density and the lower the pitting potential of the steel. The effects of Cl^-and dissolved oxygen concentrations are highly related to the temperature. When the temperature is relatively low (T < 150℃), relationships between the Cl^-and dissolved oxygen concentrations and corrosion current density of the steel are hardly observed, although the pitting potential decreases with increasing Cl^-concentration and decreasing dissolved oxygen concentration. As the temperature increases, the dependence of pitting potential on the Cl^-and dissolved oxygen concentrations disappears (at T > 130℃ and T > 150℃, respectively), and the corrosion current density increases with increasing Cl^-and dissolved oxygen concentrations. The electrochemical impedance spectroscopy (EIS) measurements and oxide film observations further confirmed these experimental results.