The Structure and Composition of Corrosion Product Film and its Relation to Corrosion Rate for Carbon Steels in CO2 Saturated Solutions at Different Temperatures

For carbon steels immersed in CO2 saturated solutions at different temperatures, the structure and the composition of corrosion product film formed on the steel surface were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The corrosion rate of the steel was evaluated by potentiodynamic polarization, and the relation between the corrosion rate and the film property was discussed. The corrosion rate of the steel was very closely associated with the structure and the composition of corrosion product film, which were affected significantly by the solution temperature. From 30 to 60 ºC, the corrosion product film composed of FeCO3 was porous and poorly adherent, and the corrosion rate increased with the rise of temperature. At 70 and 80 ºC, the corrosion product film was also composed of FeCO3 and presented a compact and dense cubic crystal structure, resulting in the decrease on the corrosion rate. The corrosion rate increased once again when the temperature was up to 90 ºC, which was attributed to the negative effect of high temperature water vapor corrosion on the grain coarsening and the part exfoliation for the FeCO3 film.

针对浸泡于二氧化碳饱和溶液中、处于不同温度环境下的碳素钢，研究人员借助扫描电子显微镜（scanning electron microscope，SEM）、X射线衍射（X-ray diffraction，XRD）及X射线光电子能谱（X-ray photoelectron spectroscopy，XPS），对其表面生成的腐蚀产物膜的结构与组成进行了系统研究。通过动电位极化法对该钢材的腐蚀速率进行了评估，并探讨了腐蚀速率与腐蚀产物膜性能之间的内在关联。研究发现，钢材的腐蚀速率与腐蚀产物膜的结构和组成密切相关，而溶液温度会显著影响该膜的特性。在30℃至60℃区间内，腐蚀产物膜以碳酸亚铁（FeCO3）为主要成分，呈现多孔且附着性欠佳的形貌，此时腐蚀速率随温度升高而逐步提升。当温度升至70℃与80℃时，腐蚀产物膜仍以FeCO3为主要成分，却呈现出致密规整的立方晶体结构，进而使得腐蚀速率显著降低。当温度进一步升高至90℃时，腐蚀速率再次出现回升，这主要归因于高温水蒸气环境对FeCO3膜的晶粒粗化及部分剥落所产生的负面影响。