腐蚀产物膜对X80钢在库尔勒土壤模拟溶液中腐蚀行为的影响

采用扫描电镜和X射线衍射对X80钢在库尔勒土壤模拟溶液中浸泡1个月后的表面腐蚀产物膜进行观察和测试,通过动电位极化和交流阻抗等电化学方法研究了腐蚀产物膜对X80钢腐蚀行为的影响。结果表明:腐蚀产物膜明显加速了X80钢在模拟溶液中的阴极还原过程,腐蚀也由原来的活化控制转变为扩散过程控制。腐蚀产物膜可分内外两层,外层产物膜由Fe2O3,Fe(OH)3和FeO(OH)组成,疏松,易脱落,没有保护作用。内层产物膜为Fe3O4,与基体结合得虽然较为紧密,但存在着微裂纹和微小孔洞等缺陷,这些缺陷增大了阴极还原的有效面积,减少了荷电离子的传输阻力,促进了腐蚀微电池的形成,从而使覆盖有腐蚀产物膜的X80钢表现出更大的腐蚀速率。

Effect of Corrosion Product Films on Corrosion Behavior of X80 Pipeline Steel in Ku'erle Soil Simulated Solution

The corrosion product films were formed on the surface of X80 pipeline steel immersed in Ku’erle soil simulated solution for 1 month,and the micrographs,compositions were observed and tested using scanning electron microscopy(SEM) and X-ray diffraction(XRD),respectively.The effect of corrosion product films on the corrosion resistance of X80 steel in simulated solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) measurements.The results showed that the corrosion product films accelerated the cathodic reduction processes,which were translated from activation control into diffusion control.The corrosion product is mainly composed of inner Fe3O4 layer and outer Fe2O3,Fe(OH)3 and FeO(OH) layer.The outer layer,which is loose and caducous,does not protect X80 from corrosion.There are some microcracks and microvoids in the inner corrosion product,which is compact,and these defects increase the effective area of cathodic reduction,reduce the transfer resistance of charge ions,promote the formation of corrosion microcell,thus,X80 steel with corrosion product films exhibits a higher corrosion rate than bare steel in Ku’erle soil simulated solution.