锈层下碳钢和耐候钢的微区和宏观腐蚀电化学行为

Corrosion Micro-and Macro-electrochemical Behavior of Rusted Carbon Steel and Weathering Steel

采用扫描电化学显微镜(SECM),辅以极化曲线和电化学阻抗谱(EIS),并结合SEM和XRD研究了耐候钢和碳钢在干湿交替环境下的腐蚀行为,包括微区阳极溶解过程和阴极还原行为、宏观腐蚀过程和微观结构及组成等.SECM测试结果表明,锈层下碳钢和耐候钢的腐蚀过程都受阳极控制,锈层的存在促进氧的还原.宏观和微区电化学测试结果均表明,在实验周期内,初期形成的锈层降低了Fe阳极溶解速率,从而提高碳钢和耐候钢的耐蚀性能,后期形成的锈层由于其组成和结构特征的变化,2种钢的腐蚀速率增加;同时耐候钢的腐蚀速率较碳钢大,且氧还原也较碳钢强,有利于锈层的形成,从而有利于长期的防护,但是耐候钢的锈层在短期内并没有很好的保护性.锈层不够致密,呈疏松多孔状,其组成主要有晶态的γ-FeOOH,Fe3O4和γ-Fe2O3等,相同的干湿循环条件制备的耐候钢锈层较碳钢厚.

Scanning electrochemistry microscope（SECM） was used to investigate corrosion behavior of carbon steel and weathering steel under wet/dry cycle conditions, combined with polarization curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The corrosion process of rusted carbon steel and weathering steel are subjected to the anodic dissolution of Fe, and the existence of rust layer promotes the reduction of oxygen. Both macro-electrochemical and SECM test show that in the experimental period, the formation of the rust layer in the initial stage reduces the anodic dissolution rate, thereby improves the corrosion resistance of carbon steel and weathering steel, while the rust layer forma tion in the later period of the experimental results in the increase of corrosion rate due to the changes of its composition and structural characteristics. The corrosion rate of weathering steel and the oxygen reduction rate are higher than that of carbon steel, which are conducive to the formation of rust layer, thus contributing to long-term protection of steel, but the rust layer of weathering steel does not have very good protection in the short term. Rust layer is relatively loose, porous and not dense enough, and the main composition of rust layer is crystalline T-FeOOH, Fe3O4 and y-Fe2O3.