J55钢在模拟海水中不同流速下的腐蚀机理研究

发布时间：2018-12-27 20:05

【摘要】：本论文以J55钢级套管材料为基材,研究在模拟海水腐蚀中流动加速腐蚀的机理,弄清溶液流动速率对腐蚀过程的影响,运用动电位极化曲线、电化学阻抗谱等电化学方法和浸泡试验研究溶液流速对J55钢腐蚀性能的影响,为流动溶液中J55套管材料的腐蚀评估提供依据。电化学测试结果表明:当流速在0~1m/s的范围内,J55碳钢在模拟海水的溶液中随着溶液流速的增大,阴极反应速率增加,稳定的开路电位和腐蚀电位正移,腐蚀电流密度增大,双电层的极化电阻降低。另一方面,阴极反应加速的同时会导致阳极反应的加速,最终导致试样腐蚀的加剧。溶液流动对J55钢阳极溶解的机制没有明显影响,但是会提高阴极Tafel常数的值,使得阴极反应的Tafel斜率值升高。同时随着溶液流速的增大,自腐蚀电流密度也明显增大,即加速了腐蚀过程。溶液流速的增大的同时也降低了J55钢的极化电阻,同时电荷传递电阻Rct在减小,Qdl在增大,可见流速主要增加了双电层的电容值,降低了双电层的电阻值。流动溶液中腐蚀产物层的fQ值较静止溶液中的fQ值小,表示流动可促进腐蚀产物从试样表面的脱离,从而具有较低的fR值。腐蚀失重测试结果表明:与静态相比,在动态腐蚀条件下,J55碳钢存在点腐蚀,腐蚀速率为严重腐蚀等级,溶液流速的增大,极大的促进了腐蚀的过程。同时,由于溶液流动增加了浓度梯度,所以J55钢在溶液流速增大时具有更高的腐蚀电流密度和更高的腐蚀速率。腐蚀机理分析表明:提高溶液的流速,加速了溶液中氧向试样表面的扩散,阴极反应速率增加,加速了钢表面的阴极反应过程,同时阴极反应加速会导致阳极反应的加速,最终导致试样腐蚀的加剧。溶液流动的加速不仅提高了J55碳钢的均匀腐蚀速率,并且增加了阴极离子的传递过程,减小了腐蚀产物膜的电阻。
[Abstract]:In this paper, the mechanism of accelerated corrosion by flow in simulated seawater corrosion was studied, and the effect of solution flow rate on corrosion process was investigated by using J55 steel casing material as substrate, and the potentiodynamic polarization curve was used. The influence of solution flow rate on corrosion performance of J55 steel was studied by electrochemical impedance spectroscopy and immersion test, which provided the basis for corrosion evaluation of J55 casing material in flowing solution. The electrochemical test results show that when the flow rate is in the range of 0~1m/s, the cathodic reaction rate of J55 carbon steel increases with the increase of the flow rate of the solution in simulated seawater, the steady open circuit potential and corrosion potential shift positively, and the corrosion current density increases. The polarization resistance of the double layer is reduced. On the other hand, the accelerated cathodic reaction will lead to the acceleration of the anodic reaction, and eventually lead to the corrosion of the sample. The solution flow has no obvious effect on the anodic dissolution mechanism of J55 steel, but it can increase the Tafel constant of the cathode and increase the Tafel slope of the cathodic reaction. At the same time, with the increase of the flow rate of solution, the corrosion current density increases obviously, that is to say, the corrosion process is accelerated. At the same time, the polarization resistance of J55 steel is decreased with the increase of solution flow rate, while the charge transfer resistance (Rct) is decreased and the Qdl is increased. The visible flow rate increases the capacitance of the double layer and decreases the resistance of the double layer. The fQ value of the corrosion product layer in the flowing solution is smaller than that in the stationary solution, indicating that the flow can promote the removal of the corrosion product from the surface of the sample, thus having a lower fR value. The results of corrosion weightlessness test show that under dynamic corrosion conditions, the corrosion rate of J55 carbon steel is serious and the corrosion rate is serious. The increase of solution flow rate greatly promotes the corrosion process. At the same time, the solution flow increases the concentration gradient, so J55 steel has higher corrosion current density and higher corrosion rate when the solution flow rate increases. The corrosion mechanism analysis shows that increasing the flow rate of the solution accelerates the diffusion of oxygen in the solution to the sample surface, increases the cathodic reaction rate, accelerates the cathodic reaction process on the steel surface, and accelerates the cathodic reaction, which leads to the acceleration of the anodic reaction. Finally, the corrosion of the specimen is aggravated. The acceleration of solution flow not only increases the uniform corrosion rate of J55 carbon steel, but also increases the cathodic ion transfer process and reduces the resistance of corrosion product film.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG172.5

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