压水堆一回路主管道316 L不锈钢的电化学腐蚀行为

通过中心复合设计试验法设计试验,结合动电位极化曲线和电化学阻抗谱的测量以及氧化膜形貌观察和成分测量,研究了温度(30~350℃)、Cl-质量浓度(10~1000μg·L-1)和溶解氧质量浓度(0~200μg·L-1)3种因素对压水堆一回路主管道316L不锈钢电化学腐蚀性能的影响.结果表明:温度是影响316L不锈钢电化学腐蚀性能最显著的因素,温度越高,腐蚀电流密度越大,点蚀电位越低;Cl-浓度和溶解氧浓度对316L不锈钢电化学腐蚀性能的影响与温度密切相关,温度较低时(T<150℃),Cl-浓度和溶解氧浓度均对316L腐蚀电流密度几乎无影响,但点蚀电位却随Cl-浓度增加和溶解氧浓度的降低而降低;温度较高时,分别为T>130℃和T>150℃,Cl-浓度和溶解氧浓度均对316L点蚀电位几乎无影响,但腐蚀电流密度却随Cl-和溶解氧的浓度增加而显著增加,腐蚀加剧.电化学阻抗谱的测量和氧化膜形貌的观察也进一步验证了上述试验结果.

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

The effects of temperature and Cl- and dissolved oxygen ( DO) concentrations on the electrochemical corrosion behav-iors of 316L stainless steel used in pressurized water reactor primary pipes were investigated via a composite design strategy, potentio-dynamic 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.