沿海核电站三种典型金属材料的常温腐蚀电化学行为

Electrochemical Behavior of Corrosion at Normal Temperature of Three Typical Metals in Coast Nuclear Power Plants

采用电化学方法研究了用于压水堆(PWR)核电站的三种典型金属结构材料,即低合金钢16MND5、不锈钢管材Z2CND18-12N和不锈钢焊缝金属308L在30℃模拟PWR一回路水溶液、掺入10mg/L Cl-的模拟PWR一回路水溶液和3.5%(质量分数)NaCl溶液中的腐蚀行为。对比分析了溶液介质、氧和材料因素对腐蚀行为的影响。结果表明:在模拟PWR一回路水溶液中,三种材料都显示出钝化特征,腐蚀敏感性较小;在溶液中加入10 mg/L Cl-后,两种不锈钢的腐蚀行为没有显著变化,低合金钢16MND5的腐蚀速率明显提高,呈现活化极化控制的活性溶解特征。在3.5%NaCl溶液中,三种材料的腐蚀敏感性显著增强,其中低合金钢16MND5的全面腐蚀速率增大,两种不锈钢的钝化区缩小即点蚀敏感性显著增大,不锈钢Z2CND18-12N的点蚀抗力明显高于不锈钢308L,不同位向的不锈钢308L焊缝的点蚀抗力没有明显差别。空气饱和条件下溶液中充入丰富的氧后,三种材料的腐蚀敏感性增强,特别是低合金钢16MND5的腐蚀敏感性增强显著。

The corrosion behavior in three solutions at 30 ℃ of three typical important structural materials used in coastal pressurized water reactor （PWR） nuclear power plants were studied by electrochemical methods. The effects of solution and material factors were analyzed. The three materials were low alloy steel 16MNDS, stainless steel weld metal 308L and stainless steel base metal Z2CND18-12N. And the three solution were simulated PWR primary water, simulated PWR pninary water with 10 mg/L Cl^- and 3. 5% NaCl solution. The results showed that, in simulated PWR primary water, three materials exhibited passivity and the minimum corrosion susceptibility as compared with in other solutions. When the primary water was added with 10 mg/L Cl^-, corrosion behaviors of the two stainless steels had little change, while the corrosion rate of 16MND5 increased significantly and exhibited active dissolution controlled by polarization. Maximum corrosion susceptibilities of three materials were exhibited in 3. 5% NaCl solution. 16MND5 showed the highest rate of general corrosion. The passivity zones of the two stainless steels were relatively narrow, indicating high susceptibility to pitting. The pitting resistance of weld metal 308L with different orientations was similar and lower significantly than that of Z2CND18-12N. Exposing the test solutions to air caused increase of corrosion susceptibility of the three materials, especially the low alloy steel, due to high content of dissolved oxygen in solutions.