X65钢多因素协同腐蚀行为和腐蚀预测模型研究

Study on Multivariate Synergistic Corrosion Behavior and Corrosion Prediction Model of X65 Steel

海底管道腐蚀失效风险激增,有必要对海底管道内腐蚀行为和腐蚀速率进行研究。采用海底管道常用钢材X65钢,利用高温高压反应釜进行了六因素三水平18组正交模拟试验,研究了CO_(2)、H_(2)S、pH值、Cl^(-)、温度、流速等服役环境因素对X65钢的协同腐蚀行为,确定了腐蚀主控因素为CO_(2)分压>H_(2)S分压> Cl~-浓度>pH值>流速>温度。基于扫描电镜检测结果,明确了H_(2)S、CO_(2)与Cl^(-)的协同腐蚀行为,CO_(2)形成致密的FeCO_(3)位于腐蚀产物膜底部,表面为Fe的硫化物,Cl^(-)穿过腐蚀产物膜层,促进腐蚀的发生。最后基于正交试验数据,建立了六因素腐蚀速率预测模型,预测误差在20%以内。

The risk of corrosion failure of submarine pipeline increases sharply, and it is necessary to study the corrosion behavior and corrosion rate of submarine pipeline. In this work, 18 groups of six factors and three-level orthogonal experiments were carried out for the submarine pipelines commonly used steel X65 steel in high temperature and high pressure reactors. The synergistic corrosion behavior of X65 steel by CO_(2), H_(2)S, pH value, Cl^(-), temperatures and flow rates was studied, and the main controlling factors for corrosion were determined as CO_(2) partial pressure H_(2)S partial pressure Cl^(-) concentration pH value flow rate temperature. From the results of scanning electron microscope, the synergistic corrosion behavior of H_(2)S, CO_(2) and Cl^(-) was clarified: CO_(2) formed dense FeCO_(3), which was located at the bottom of the corrosion product film, and the surface was Fe sulfide. Moreover, Cl^(-) passed through the corrosion product film to promote the occurrence of corrosion. Finally, based on the orthogonal experimental data, a six-factor corrosion rate prediction model was established, and the prediction model error was less than 20%.