20#钢在CO2/H2O气液两相塞状流中的腐蚀行为

采用自主设计动态腐蚀实验装置研究20#钢在CO2/H2O两相塞状流条件下的腐蚀行为，利用失重法、SEM、EDS和XRD等手段对腐蚀试样进行腐蚀速率分析、腐蚀形貌观察以及腐蚀产物成分与膜层结构特征分析.结果表明：随时间的延长腐蚀速率呈先小幅减小、后快速增大、再明显降低的趋势，4h和8h分别达实验条件下的最大值(2.074 6 mm/a)和最小值(1.898 8 mm/a)；下管壁腐蚀形貌特征表明随时间延长腐蚀产物膜层由初始阶段疏松团絮状产物+细小针状产物组成含有微裂纹的单层腐蚀产物膜层逐渐转变为双层腐蚀产物膜，外层膜疏松其具有贯穿性裂纹，而内层膜相对致密并随时间延长致密度逐渐提高，EDS分析结果表明内层相对致密膜层的铁含量高于外层膜，属于富铁腐蚀产物，外层相对疏松膜层的碳氧元素含量之和相比内层膜较高；在同时间段上管壁腐蚀产物沿垂直流动方向呈条带状分布，由初始粗大疏松产物颗粒逐渐转变为具有规则排列特征的晶粒；腐蚀产物主要由Fe、C、O三种主要元素组成，主要组成相有Fe3C、FeCO3、Fe3O4、FeOOH.
The corrosion behavior of 20# steel was studied under CO2/H2O two phase plug flow condition using self-designed experiment device. The corrosion rate, corrosion appearance, the composition of corrosion products and the structure characteristics of film were investigated through weight loss method, scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and X-Ray diffraction (XRD), respectively. The results show that the trend of corrosion rate first slightly decreases followed by a rapid increase, and then dramatically decreases with the increasing of corrosion time. The maximum (2.074 6 mm/a) and minimum (1.898 8 mm/a) value reached at 4 h and 8 h, respectively. The corrosion characteristics of corrosion products on the bottom pipe wall by the beginning of the single layer of loose flocculent and tine needle product change into double films of corrosion product gradually. The outer layer with micro-crack is loose, but the inner is relatively dense and its density is increasing with time. The EDS analysis results confirm that the inner dense layer belongs to rich iron product because the Fe content is higher than that of outer layer, and the content of C/O elements in outer loose layer is relatively high. At the same time period the corrosion products at the top wall of pipe are a zonal distribution along the vertical direction of flow, and the bulky loose particles at initial stage gradually transform into crystal grain with regular arrangement. Corrosion products mainly consist of Fe, C, O and the composition mainly includes Fe3C, FeCO3, Fe3O4 and FeOOH.