發(fā)布時(shí)間：2018-12-27 20:05

【摘要】：本論文以J55鋼級(jí)套管材料為基材,研究在模擬海水腐蝕中流動(dòng)加速腐蝕的機(jī)理,弄清溶液流動(dòng)速率對(duì)腐蝕過(guò)程的影響,運(yùn)用動(dòng)電位極化曲線、電化學(xué)阻抗譜等電化學(xué)方法和浸泡試驗(yàn)研究溶液流速對(duì)J55鋼腐蝕性能的影響,為流動(dòng)溶液中J55套管材料的腐蝕評(píng)估提供依據(jù)。電化學(xué)測(cè)試結(jié)果表明:當(dāng)流速在0~1m/s的范圍內(nèi),J55碳鋼在模擬海水的溶液中隨著溶液流速的增大,陰極反應(yīng)速率增加,穩(wěn)定的開路電位和腐蝕電位正移,腐蝕電流密度增大,雙電層的極化電阻降低。另一方面,陰極反應(yīng)加速的同時(shí)會(huì)導(dǎo)致陽(yáng)極反應(yīng)的加速,最終導(dǎo)致試樣腐蝕的加劇。溶液流動(dòng)對(duì)J55鋼陽(yáng)極溶解的機(jī)制沒有明顯影響,但是會(huì)提高陰極Tafel常數(shù)的值,使得陰極反應(yīng)的Tafel斜率值升高。同時(shí)隨著溶液流速的增大,自腐蝕電流密度也明顯增大,即加速了腐蝕過(guò)程。溶液流速的增大的同時(shí)也降低了J55鋼的極化電阻,同時(shí)電荷傳遞電阻Rct在減小,Qdl在增大,可見流速主要增加了雙電層的電容值,降低了雙電層的電阻值。流動(dòng)溶液中腐蝕產(chǎn)物層的fQ值較靜止溶液中的fQ值小,表示流動(dòng)可促進(jìn)腐蝕產(chǎn)物從試樣表面的脫離,從而具有較低的fR值。腐蝕失重測(cè)試結(jié)果表明:與靜態(tài)相比,在動(dòng)態(tài)腐蝕條件下,J55碳鋼存在點(diǎn)腐蝕,腐蝕速率為嚴(yán)重腐蝕等級(jí),溶液流速的增大,極大的促進(jìn)了腐蝕的過(guò)程。同時(shí),由于溶液流動(dòng)增加了濃度梯度,所以J55鋼在溶液流速增大時(shí)具有更高的腐蝕電流密度和更高的腐蝕速率。腐蝕機(jī)理分析表明:提高溶液的流速,加速了溶液中氧向試樣表面的擴(kuò)散,陰極反應(yīng)速率增加,加速了鋼表面的陰極反應(yīng)過(guò)程,同時(shí)陰極反應(yīng)加速會(huì)導(dǎo)致陽(yáng)極反應(yīng)的加速,最終導(dǎo)致試樣腐蝕的加劇。溶液流動(dòng)的加速不僅提高了J55碳鋼的均勻腐蝕速率,并且增加了陰極離子的傳遞過(guò)程,減小了腐蝕產(chǎn)物膜的電阻。
[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.
【學(xué)位授予單位】：西安石油大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG172.5

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