长期时效N10276合金在CO2/H2S/Cl- 环境中的腐蚀行为

Corrosion Behavior of Long-Term Aged N10276 Alloy in CO2/H2S/Cl- Environments

摘要:

通过电化学阻抗与循环动电位极化的方法研究了在CO₂/Cl^-以及CO₂/H₂S/Cl^-溶液体系中、长期时效前后N10276合金的腐蚀机理。结果表明，阻抗弧的低频区间出现了一个不完整的容抗弧，并且随H₂S浓度的增加（10~100 μL/L）转变为Warburg阻抗，其主要原因是高含量H₂S相关吸附物。H₂S可以增加合金腐蚀速率。相比较而言，长期时效处理主要作用于合金点蚀的形成，其中，经过长期时效处理的奥氏体组织内存在大量的第二相（富含Mo与Ni的μ相），而析出物周围的区域成为优先腐蚀区域，进而导致了N10276合金点蚀的发生。

Abstract:

The corrosion mechanism of the N10276 alloy before and after long-term aging treatment in aqueous solutions containing CO₂/Cl^- and CO₂/H₂S/Cl^- was studied through the electrochemical impedance plots and cyclic potentiodynamic polarization. Results reveal that a not-well-defined capacitive loop appears in the low-frequency range and it changes into Warburg's impedance as the H₂S concentration increases (10~100 μL/L) due to the large quantities of H₂S-related adsorbed species in the film. In addition, H₂S concentration plays a key role in increasing corrosion rate. In comparison, the action of long-term aging is more significant on pitting corrosion. The surrounding sites of the precipitates become the preferred corrosion area since the austenite microstructure of long-term aged N10276 alloy includes lots of precipitated second phases (μ phase with accumulation of Mo and Ni elements), leading to the occurrence of pitting defects.