X70管线钢在含CO_2湿天然气环境下腐蚀行为

CO_2 corrosion behavior of X70 pipeline steel in wet gas environment

利用高温高压冷凝釜模拟油气田湿天然气CO2腐蚀环境,进行了不同气体温度、湿气-管壁温差的湿气冷凝腐蚀实验,研究了温度对X70钢腐蚀形态、速率的变化规律.利用扫描电镜和能谱仪,分析了腐蚀产物膜的微观形貌和成分,并与高温高压釜中全水相实验结果进行了对比.建立了湿气管道腐蚀预测模型,初步探讨了湿气温度、管壁温度、温差、液膜温度和冷凝率等重要湿气参数对湿气顶部腐蚀的影响.结果表明:在相同管壁温度(5℃)下,湿气温度升高使X70管线钢腐蚀速率升高;在相同的湿气温度(25℃和45℃)下,X70钢的腐蚀速率随管壁温度的升高而略有下降;在20～45℃范围内,腐蚀产物膜与基体的结合较弱,极易从基体剥落,腐蚀形态均为全面腐蚀.

With a high-temperature and high-pressure condensation autoclave simulating the circumstance of CO2 corrosion in wet gas pipelines,the variation in corrosion behavior and morphology of X70 pipeline steel was studied by changing the wet gas temperature and the temperature difference between the wet gas and the pipe wall.Scanning electron microscopy（SEM） and energy dispersive spectrometry（EDS） were employed to analyze the morphologies and characteristics of corrosion scales on the steel.The results were compared with those under solution-immersed conditions in a high-temperature and high-pressure autoclave.Using a corrosion prediction model,the influence of some important parameters on corrosion at the top of wet gas pipelines were preliminary studied,such as wet gas and pipe wall temperatures,temperature difference,condensed liquid film temperature and condensation rate.The results show that at the same temperature of the pipe wall（5℃）,the corrosion rate increases with the wet gas temperature rising;while at the same temperature of wet gas（25℃ and 45℃）,the corrosion rate decreases slightly with the pipe wall temperature rising.In the temperature range of 20 to 45℃,corrosion scales are easily peeled off from the substrate,and uniform corrosion is the predominant morphology.