高氮耐候钢锈层的电化学与物相表征

为了考察氮元素对耐候钢耐腐蚀性能的影响,研究制备了氮质量分数分别为0.0358%和0.0026%的高氮耐候钢和低氮耐候钢。应用电化学阻抗谱和X射线衍射(XRD)分析、电子探针(EPMA)面扫描技术研究了两种实验钢在模拟工业大气溶液中腐蚀电化学过程和锈层结构的异同。电化学阻抗谱显示,高氮耐候钢在高频段(点蚀诱发期)比传统耐候钢有着更加优良的耐点蚀能力,低频段(扩散型阻抗生成期)则显示腐蚀产物层具有更高的阻抗,抵御腐蚀介质侵蚀的能力较强。X射线衍射和电子探针分析结果表明耐候钢高氮含量促进了稳定结构锈层生成,锈层中非晶态α-(Fe_1-xCr_x)OOH的分布更广泛、连续,提升了耐候钢抵御Cl^-侵入的能力。高氮钢腐蚀坑具有大宽深比的特征,内锈层较薄,证明其具有良好的抑制点蚀能力。

Electrochemical and phase characterization of rust layer on high nitrogen weathering steel

In order to investigate the influence of nitrogen on corrosion resistance property of weathering steel, the high nitrogen and low nitrogen weathering steels were prepared with nitrogen mass fraction of 0.0358% and 0.0026%, respectively. The process of corrosion electrochemistry and the structure of rust layer in simulated industrial atmosphere were studied and compared between two experimental steels by electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) analysis and electron probe microanalysis technique (EPMA). The EIS results indicated that the high nitrogen weathering steel exhibited better pitting corrosion resistance property than the traditional weathering steels at high frequency stage (pitting generating). Moreover, the corrosion product layer of high nitrogen weathering steel had higher impedance at low frequency stage (diffusion impedance acting), suggesting the strong resistance to corrosive medium. The analysis results of XRD and EPMA showed that the high content of nitrogen in weathering steel promoted the generation of rust layer with stable structure. The distribution of amorphous α-(Fe_1-xCr_x)OOH in rust layer was more widespread and continuous, which enhanced the ability to resist the erosion of Cl^- in weathering steel. The corrosion pits in high nitrogen steel had large width to depth ratio. The inner rust layer was relatively thin, indicating that it exhibited good ability to inhibit pitting.