本文選題：X80鋼 + SO_4~(2?)　； 參考：《南昌航空大學》2017年碩士論文

【摘要】：“西氣東輸”管線約1/5跨越酸性紅壤區(qū)域,X80管線鋼在紅壤環(huán)境中的腐蝕失效是影響其使用壽命、使用安全的重要問題。目前,關于管線鋼紅壤腐蝕的環(huán)境因素,如腐蝕性離子的作用、腐蝕產物膜的影響及涂層破裂時液膜下的腐蝕行為,均尚無深入研究。因此,研究管線鋼在不同條件的紅壤模擬液及薄液膜中的腐蝕行為十分必要。本文通過動電位極化法、電化學阻抗譜、三維視頻顯微鏡、掃描電子顯微鏡(SEM)等手段研究了土壤中腐蝕性離子SO_4~(2-)的含量、腐蝕產物膜對X80鋼在紅壤模擬溶液中腐蝕行為的影響,同時,探討了涂層破裂下紅壤模擬液膜pH值對X80鋼電化學腐蝕的作用。研究結果表明,在酸性紅壤模擬溶液中,X80鋼的腐蝕速率隨SO_4~(2-)濃度變化而明顯變化;在含1%~5%SO_4~(2-)的模擬液中,SO_4~(2-)會阻礙腐蝕性離子Cl-在電極表面的吸附,從而減緩腐蝕,此時X80鋼的腐蝕速率隨SO_4~(2-)濃度增加而減小;當SO_4~(2-)質量分數(shù)大于5%后,高濃度的SO_4~(2-)會破壞電極表面膜的形成,此時腐蝕速率隨SO_4~(2-)濃度升高而增加。在含1%~10%SO_4~(2-)的酸性紅壤模擬液中,X80鋼的EIS均呈現(xiàn)出高頻容抗弧和低頻感抗弧。由腐蝕失重量及腐蝕極化曲線分析可知,腐蝕產物膜的厚度與結構對X80鋼的腐蝕速率有顯著影響。當X80鋼在紅壤模擬液中浸泡4d時電極表面形成了較為完整的初期腐蝕產物膜,該產物膜具有保護性,此時腐蝕速率最低。隨著浸泡時間增加,X80鋼表面覆有中期腐蝕產物膜,產物膜分為內外兩層,外層產物膜疏松呈暗黃色,內層較薄呈黑色;此時腐蝕產物膜保護性很差,腐蝕速率出現(xiàn)較大幅度的上升。當浸泡時間為30d時,試樣表面覆有后期腐蝕產物膜,膜層厚度有所增加,產物膜更加疏松多孔,溶液中的腐蝕性離子容易進入金屬基體表面與之發(fā)生反應,使腐蝕速率加快,此時腐蝕產物膜保護性較弱。結合不同厚度、不同pH值的紅壤模擬液膜下X80鋼的腐蝕電化學數(shù)據(jù)及腐蝕形貌分析表明,液膜厚度為80μm、pH=4時,X80鋼腐蝕受腐蝕產物膜及氧氣擴散的共同影響,X80鋼腐蝕速率最小;pH值升至5~7時,氧還原控制腐蝕過程,X80鋼的腐蝕速率小幅增加。液膜厚度繼續(xù)增加后,即厚度為110μm、280μm、1000μm時,X80鋼的腐蝕速率隨著pH值的增大而減小,此與在本體溶液中所得結果相一致。
[Abstract]:The corrosion failure of X80 pipeline steel in red soil environment is an important problem affecting its service life and safety. At present, the environmental factors of pipeline steel red soil corrosion, such as the effect of corrosive ions, the effect of corrosion product film and the corrosion behavior under the liquid film when the coating is ruptured, have not been thoroughly studied. Therefore, it is necessary to study the corrosion behavior of pipeline steel in red soil simulated liquid and thin liquid film under different conditions. By means of potentiodynamic polarization, electrochemical impedance spectroscopy, 3D video microscope, scanning electron microscope (SEM) and so on, the content of corrosive ion so _ 4H _ 2O _ 2-in soil and the effect of corrosion product film on corrosion behavior of X80 steel in simulated solution of red soil were studied in this paper. At the same time, the effect of pH value of simulated liquid film on the electrochemical corrosion of X80 steel was studied. The results show that the corrosion rate of X80 steel varies significantly with the concentration of so _ 4 ~ (2) in the simulated solution of acidic red soil, and that in the simulated solution containing 1 ~ (5) so _ (4) ~ (2), it will hinder the adsorption of corrosive ion Cl- on the electrode surface, thus slowing down the corrosion. At this time, the corrosion rate of X80 steel decreases with the increase of so _ 4N _ 2-concentration, and when the mass fraction of so _ 4N _ (2) is more than 5%, the formation of electrode surface film will be destroyed by the high concentration of so _ 4 ~ (+) _ (2), and the corrosion rate will increase with the increase of so _ (4) ~ (2) concentration. The EIS of X80 steel in the acid red soil simulation solution containing 1 / 10SO4 / 2) showed high frequency capacitive and low frequency inductive reactance. According to the analysis of corrosion weight loss and corrosion polarization curve, the thickness and structure of corrosion product film have significant influence on the corrosion rate of X80 steel. When X80 steel was immersed in red soil simulated solution for 4 days, the surface of the electrode formed a relatively complete initial corrosion product film, the product film was protective, and the corrosion rate was the lowest. With the increase of soaking time, the surface of X80 steel is covered with intermediate corrosion product film, the product film is divided into two layers, the outer layer is loose and yellow, the inner layer is thin and black, and the protection of corrosion product film is very poor. The corrosion rate increased greatly. When the soaking time is 30 days, the surface of the sample is covered with the late corrosion product film, the thickness of the film increases, the product film is more loose and porous, and the corrosive ions in the solution can easily enter the metal substrate surface and react with it, so the corrosion rate is accelerated. At this time, the corrosion product film is less protective. The corrosion electrochemical data and corrosion morphology of X80 steel under simulated liquid film of red soil with different thickness and different pH value were analyzed. When the thickness of liquid film is 80 渭 m 路m ~ (-1) and pH = 4, the corrosion rate of X80 steel is affected by corrosion product film and oxygen diffusion. The minimum pH value of corrosion rate of X80 steel rises to 5 ~ 7, and the corrosion rate of X80 steel increases slightly in the process of oxygen reduction controlled corrosion. The corrosion rate of X80 steel decreases with the increase of pH value when the thickness of liquid film continues to increase, that is, when the thickness is 110 渭 m ~ 280 渭 m ~ (-1) 渭 m, which is consistent with the results obtained in bulk solution.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG178

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