高含CO_(2)低含H2S条件下温度对P110碳钢腐蚀规律的影响

Effect of Temperature on Corrosion of Pl10 Steel in Oil Field Environment with High CO_(2) and Low H2S

为了明确高含CO_(2)及少量H2S条件下,温度变化对石油管材P110钢腐蚀速率的影响,利用高温高压硫化氢反应釜开展了腐蚀模拟试验,利用失重法记录腐蚀速率。应用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和激光共聚焦显微镜等,研究并分析了P110钢表面的腐蚀形貌和产物。结果表明:在1 MPa CO_(2)分压、20 kPa H2S分压和流速1 m/s条件下,P110钢管材均匀腐蚀速率随温度升高先增大后减小,在100℃附近达到峰值。当温度超过80℃时,P110钢表面腐蚀形态由全面腐蚀转变为局部腐蚀。随着温度的升高,P110钢表面腐蚀产物由富铁结构转变为富硫结构,致密的陨硫铁矿和磁黄铁矿阻碍腐蚀反应的离子扩散。此外,在60~100℃,温度升高会同时促进阴极反应和阳极反应,导致P110钢自腐蚀电流密度增加,腐蚀速率提高,而当温度继续由100℃升高至120℃时,P110钢自腐蚀电流密度减小,腐蚀过程逐渐受到抑制。

In order to clarify the influence of temperature on the corrosion rate of Pll0 steel under high CO_(2) and low H_(2)S conditions,corrosion simulation experiments were carried out and the corrosion rate was recorded by weight loss method.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and laser confocal microscope were used to observe and analyze the corrosion morphology and corrosion products on the surface of Pllo steel.The results showed that the general corrosion rate of Pllo steel increased and then decreased with the increase of temperature under the condition with CO_(2) partial pressure of 1 MPa and H2S partial pressure of 20 kPa.The corrosion peak temperature was reached near 100℃.When the temperature rised above 80℃,the corrosion morphology changed from general corrosion to localized corrosion and the corrosion pits could be observed within 80℃ to 12℃.With the increase of temperature,the corrosion products on the surface of Pllo steel changed from iron-rich structure to sulfur-rich structure.Dense troilite and pyrrhotite impeded ion diffusion in the corrosion reaction.The increased of temperature in the range from 60℃ to 100℃ would promote the reaction of anode and cathode,which would lead to the increase of the current density and corrosion rate of Pl10 steel.When the temperature continued to rise to 12℃,the Pllo steel self-corrosion current density would decrease and the corrosion process would be inhibited.