二氧化碳腐蚀规律研究

Study on Corrosion Law of Carbon Dioxide

采用高温高压腐蚀模拟实验研究了CO2腐蚀规律,同时应用扫描电镜(SEM)研究了腐蚀产物的表面形貌和微观结构。实验结果表明,随着温度升高CO2腐蚀速率呈现增加、减小、再增加、再减小的趋势,存在两个极大值点,CO2质量浓度不同,峰值存在明显不同。当CO2质量浓度为4,6和8 g/L时,低温极大值均出现在60℃;当CO2质量浓度为4和6 g/L时,高温极大值在120℃出现,而CO2质量浓度为8 g/L时,高温极大值漂移到140℃。在低温条件下随着CO2质量浓度的增加,腐蚀速率增大,而高温下却出现一定的不确定性。这主要是由于CO2扩散、保护膜的抑制两种因素共同作用的结果。应用扫描电镜研究腐蚀产物的表面形貌和微观结构,结果显示腐蚀产物膜的完整性和致密性越好,则腐蚀速率越小,完整、致密、附着力强的稳定性膜可减少均匀腐蚀速率,而膜的缺陷、脱落则可诱发严重的局部腐蚀。

The corrosion law of CO2 was studied by high - pressure high - temperature simulation testes, and the morphology and microstructure of the CO2 corrosion products were analyzed by scanning electron microscope （SEM）. The results showed that, with the rising temperature, the corrosion rate of CO2 developed in the trend of increasing and decreasing and then increasing and decreasing again. It had two peaks in the curve. The peaks varied apparently with CO2 concentrations. The corrosion rates reached the first peak at 60 ℃ in the lower temperature range when the CO2 concentrations were 4 g/L, 6 g/L and 8 g/L. In contrast, in the upper temperature range, they reached the second peak at 120 ℃ when the CO2 concentrations were 4g/L and 6g/L, and then reached the second peak at 140 ℃ when the CO2 concentration was 8 g/L. The corrosion rate increased with increasing CO2 concentration under low temperature; Whereas, they revealed some uncertainties with increasing CO2 concentration under high temperature. This is because of synergistic function of two factors, i.e. the diffusion of COL and the corrosion resistance of protection films. The intact, compact, adhesive and protective surface films could reduce the general corrosion rate rapidly. Contrarily, the incompact and easily removable surface films could lead to serious localized corrosion.