高温高压下20钢和13Cr钢在不同含量甲酸-CO2环境中的腐蚀行为

摘要

采用腐蚀失重测试、腐蚀产物分析等方法,研究了20钢和13Cr钢在模拟油井管道环境(甲酸与CO2共存,100℃、1 MPa)中的腐蚀速率和腐蚀类型,并探讨了甲酸含量对其腐蚀行为的影响.结果表明:两种钢的腐蚀速率均随甲酸含量的增加而增大,13Cr钢的腐蚀速率低于20钢的;20钢的腐蚀类型为均匀腐蚀,13Cr钢的为点蚀;20钢表面有FeCO3的生成和碳酸盐的沉积,FeCO3产物层覆盖部位不断发生基体的溶解,而钙、镁碳酸盐沉积的位置不断出现产物沉积,在基体腐蚀相对较慢的部位形成突起;13Cr钢优先发生铬的溶解,形成以Cr(OH)3为主的钝化膜,随着甲酸含量的增加,钝化膜的稳定性、致密性均降低,H+和Cl-通过钝化膜与基体接触,促进了点蚀的发生.%The corrosion rate and corrosion type of 20 steel and 13Cr steel in simulated well pipe environment (foric acid coexisting with CO 2 ,100 ℃,1 MPa)were studied by the weight method and analyzation of corrosion product.The effect of formic acid content on corrosion behavior was discussed.The results indicate that the corrosion rate of two steels increased with increase of formic acid content,and the corrosion rate of 13Cr steel was lower than that of 20 steel.The corrosion type of 20 steel was uniform corrosion,and corrosion type of 13Cr steel was pitting.There were FeCO 3 production and carbonate deposition on the surface of 20 steel.The substrate was dissolved continuously in the position covered by FeCO 3 production,and the product was deposited continuously in the position deposited by carbonate.The position with lower corrosion rate was bulged on the surface of substrate. The dissolution of Cr occurred in 13Cr steel and passive film formed on the surface.With increase of formic acid content,the stability and density of passive film were reduced and H + and Cl- contacted with substrate through passive film which promote the occurrence of pitting.