模拟不同浓度Cl^(-)对14Cr12Ni3WMoV不锈钢电化学腐蚀行为的影响

Simulation of the Electrochemical Corrosion Behavior of 14Cr12Ni3WMoV Stainless in Different Concentrations of Cl^(-)

为了探明Cl^(-)浓度对汽轮机末级叶片常用钢腐蚀的影响,通过动电位极化法、电化学阻抗谱、Mott-Schottky曲线、激光共聚焦显微镜、扫描电镜等方法分析了在不同Cl^(-)浓度模拟溶液中14Cr12Ni3WMoV马氏体不锈钢的电化学腐蚀行为。结果表明:随着Cl^(-)浓度的不断增大,不锈钢钝化膜点缺陷增加,稳定性下降,点蚀敏感性增强,对材料基体的保护能力下降;不锈钢表面点蚀坑的孔径随着Cl^(-)浓度的增大会明显变大,但腐蚀坑的深度无明显升高,腐蚀坑更易沿材料表面发展;不锈钢发生点蚀时,材料中Fe,Cr,Ni,W,Mo,V等发生选择性溶解,Fe和Ni会以离子形式迁移至溶液中,而Cr,W,Mo,V则会以氧化物形式沉积在腐蚀坑内。

In order to analyze the effect of Cl^(-)concentration on the electrochemical corrosion of steel commonly used for the final stage blade of steam turbine,the electrochemical corrosion behavior of 14 Cr12 Ni3 WMoV martensitic stainless steel in simulated solutions with different chloride ion concentrations was investigated by various methods including potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),Mott-Schottky(M-S)curves,laser scanning confocal microscope(LSCM)and scanning electron microscope(SEM).Results showed that with the increase of Cl^(-)concentration,the point defect inside the stainless steel passivation film increased,the stability became weaker,the pit corrosion sensitivity increased and its protection ability to material substrate declined.The diameter of corrosion pit on the surface of stainless steel increased significantly with the increase of Cl^(-)concentration,but the depth of the corrosion pit did not increase significantly,indicating that corrosion pits were more likely to develop along the material surface.When pitting corrosion occurred in stainless steel,the elements of Fe,Cr,Ni,W,Mo and V of materials were selectively dissolved.Specifically,Fe and Ni migrated to the solution in the form of ions,while Cr,W,Mo and V deposited in the corrosion pit in the form of oxides.