Study on the Electrochemical Polarization and Stress Corrosion Cracking Behaviors of Alloy 690 in 5M Chloride Solutions at 25℃

690合金在25℃的5M NaCl溶液中之電化學極化與應力腐蝕行為研究

陳彥羽(Y. Y. Chen) ； 周良賓(L. B. Chou) ； 施漢章(H. C. Shih)

《防蝕工程》 19卷4期 (2005/12) Pp. 523-539

https://doi.org/10.6376/JCCE.200512.0523

摘要

An experimental, potential-pH diagram was constructed for the nickel-based Alloy 690 in 25℃ concentrated (5M) sodium chloride solution, using an cyclic polarization method. The domains of immunity, general corrosion, passivation, and pitting in 5M NaCl solutions were defined. At pH＞4 the passive region subdivided into areas of perfect passivation, imperfect passivation, and pitting. After anodic polarization, the surface of each specimen was carefully examined metallographically. Pitting corrosion was observed over the entire pH range investigated (0.3-8.52) but general corrosion predominated at lower pH values (＜3). On the other hand, the mechanical properties, such as ultimate tensile strength (UTS), strain at fracture and the reduction area (RA) measured by the slow strain rate test (SSRT), decreased significantly at pH＜3. The SSRT results are consistent with fractography and side-view observations of the tested specimens by SEM.

關鍵字

電位與pH值關係圖 ； 690合金 ； 循環極化 ； 孔蝕 ； 均勻腐蝕 ； 鈍態 ； 慢速應變拉伸試驗

並列摘要

An experimental, potential-pH diagram was constructed for the nickel-based Alloy 690 in 25℃ concentrated (5M) sodium chloride solution, using an cyclic polarization method. The domains of immunity, general corrosion, passivation, and pitting in 5M NaCl solutions were defined. At pH＞4 the passive region subdivided into areas of perfect passivation, imperfect passivation, and pitting. After anodic polarization, the surface of each specimen was carefully examined metallographically. Pitting corrosion was observed over the entire pH range investigated (0.3-8.52) but general corrosion predominated at lower pH values (＜3). On the other hand, the mechanical properties, such as ultimate tensile strength (UTS), strain at fracture and the reduction area (RA) measured by the slow strain rate test (SSRT), decreased significantly at pH＜3. The SSRT results are consistent with fractography and side-view observations of the tested specimens by SEM.

並列關鍵字

Potential-pH diagram ； Alloy 690 ； Cyclic polarization ； Pitting corrosion ； General corrosion ； Passivation, SSRT