316L不锈钢在循环水中点蚀的氯离子浓度阈值研究

Study on Critical Chlorine Ion Concentration for Pitting Corrosion of 316L Stainless Steel in Cooling Water

采用电化学法研究了316L不锈钢在循环水中的点蚀电位(Eb)、蚀孔深度和数目与Cl-质量浓度的关系。结果表明,常温下316L不锈钢的Eb总是随着Cl-质量浓度的增大而减小,当Cl-质量浓度小于900 mg/L时,增大Cl-质量浓度易导致点蚀敏感,而大于该值时增大Cl-质量浓度不会明显增大点蚀倾向;从蚀孔深度和表面蚀孔数目可以看出,随着Cl-质量浓度升高,最大蚀孔深度增大,当Cl-质量浓度较大时这种增大变缓慢;316L不锈钢在Cl-质量浓度小于1 150 mg/L时点蚀倾向对Cl-质量浓度敏感,在Cl-质量浓度大于1 150 mg/L时点蚀倾向对Cl-质量浓度不敏感,其点蚀倾向由大变小的Cl-质量浓度阈值为1 150 mg/L。

The relationship of electric potential （Eb ） , pitting depth and number of pitting corrosion of 316L stainless steel in cooling water with C1 is studied by electrochemistry. The results show that the pitting corrosion electric potential （ Eb ） goes down with the increasing chloride ion concentration in ambient temperature. When Cl- concentration is lower than 900 mg/L,further increasing the C1- concentration will concentration is higher than 900 rag/L, further increase the sensitivity of pitting corrosion. When C1- increasing the C1- concentration has no greater impact on pitting corrosion tendency. As seen from depths and number of corrosion pits, The depth of the largest corrosion pits becomes greater with rising C1- concentration, and when the C1- concentration is at the high level, the increase of depth of corrosion pits will slow down. The pitting corrosion of 316L stainless steel is very sensitive to C1 - ions at a concentration of 〈 1150mg/L and is not sensitive to C1 - ions at a concentration of 〉 ll50mg/L. The critical C1- concentration obtained by depth and number of pits is 1150 mg/L.