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采用开路电位监测、电化学阻抗谱、动电位极化曲线测量和热力学分析等方法,研究690合金在模拟压水堆二次侧高温高压碱性水环境中(氨水调节pH_(@25℃)=9.5)的电化学性能。结果表明:在不同温度下(50,100,150,200,250和285℃)的氨水溶液中浸泡20 h后,690合金的开路电位都已到达较稳定状态,表面有双层氧化膜生成。随着温度的升高,外层氧化膜阻值先减小后增加,内层氧化膜阻值逐渐减小,而总的氧化膜保护性逐渐降低。再结合实验温度下溶液pH@T的降低,导致690合金的开路电位下降,由极化曲线获得的腐蚀电流密度和维钝电流密度增加。
The open circuit potential monitoring, electrochemical impedance spectroscopy, potentiodynamic polarization curve measurement and thermodynamic analysis were used to study the effect of 690 alloy on the secondary high temperature and high pressure alkaline water environment of simulated PWR (pH = (25 ℃) 9.5) electrochemical properties. The results show that the open circuit potential of 690 alloy has reached a steady state and the surface has a double oxide film after immersed in ammonia solution at different temperatures (50, 100, 150, 200, 250 and 285 ℃) for 20 h. With the increase of temperature, the resistance of the outer oxide film first decreases and then increases, while the resistance value of the inner oxide film gradually decreases, while the overall oxide film’s resistance gradually decreases. Combined with the decrease of pH @ T at the experimental temperature, the open circuit potential of 690 alloy is decreased, and the corrosion current density and the dimension of the blunt current are increased by the polarization curve.