典型土壤环境下X100管线钢的缝隙腐蚀机理研究

发布时间：2018-04-18 17:36

本文选题：X100管线钢 + 缝隙腐蚀　；参考：《内蒙古科技大学》2015年硕士论文

【摘要】：土壤对管线钢的腐蚀不可避免，尤其是缝隙腐蚀对埋地管线钢的破坏尤其严重。缝隙腐蚀主要是由于缝内狭小空间造成内外氧浓差与氯离子迁移产生的，氯离子大量迁移到缝隙内破坏了缝内金属的钝化状态，缝隙内形成闭塞电池，并且缝内不断进行其自催化效应，使得金属严重腐蚀。本文应用模拟缝隙装置，实验选取我国江西鹰潭、新疆库尔勒、内蒙古伊盟三地具有代表性的酸性、碱性、中性土壤模拟溶液作为腐蚀介质，研究了X100管线钢在模拟缝隙装置内的缝隙腐蚀行为，并且研究了外加电流阴极保护法对缝隙腐蚀的影响，探索在酸碱中性土壤模拟环境下，X100管线钢的缝隙腐蚀规律。实验研究了X100管线钢在模拟江西鹰潭、新疆库尔勒、内蒙古伊盟土壤溶液下的缝隙腐蚀行为。实验结果表明：X100管线钢模拟缝隙试样，在鹰潭、库尔勒、伊盟土壤模拟溶液介质下，缝内溶液的Cl-浓度均随时间的延长而增加，并且在浸泡初期Cl-浓度增加迅速，浸泡时间超过20h后Cl-浓度增加较为缓慢。X100管线钢在鹰潭土壤模拟溶液、库尔勒土壤模拟溶液、伊盟土壤模拟溶液介质下，随浸泡时间的延长，缝内各位置处的电极电位E均有不同程度的降低；并且电极电位E从缝口到缝底逐步降低，说明缝底处腐蚀最为严重。实验研究了X100管线钢在缝隙内部的阴极极化特点，研究了极化时间、缝口阴极极化控电位、不同介质等因素对缝内极化电位的影响趋势，并分析了在阴极保护条件下三种介质下X100管线钢的缝隙腐蚀的程度。结果表明：X100管线钢模拟缝隙试样，在鹰潭、库尔勒、伊盟土壤模拟溶液介质下，缝口通入-1000mVCS极化电压，随极化时间的延长，缝内各位置处的极化电位均呈梯度下降趋势；在同一极化时间下，缝口到缝底极化电位呈一定梯度的增加趋势，并且随极化时间的延长，缝口到缝底的极化电位变化梯度越不明显；X100管线钢模拟缝隙试样，在鹰潭、库尔勒、伊盟土壤模拟溶液介质下，，随着缝口通入控制电位的降低，缝内各位置处的极化电位均呈现一定梯度的负移现象；当极化电位为-1000mVCSE、-1150mVCSE时，缝内各位置处极化电极均在临界保护电压以下，均达到阴极保护效果；当缝口电压为-850mVCSE时，鹰潭土壤模拟溶液介质下，缝底深处为处于欠保护状态。
[Abstract]:Soil corrosion to pipeline steel is inevitable, especially crevice corrosion to buried pipeline steel.Slot corrosion is mainly caused by the oxygen concentration difference and chloride ion migration in the narrow space of the gap. The chloride ions migrate to the gap to destroy the passivation state of the metal in the gap, and the closed cell is formed in the gap.And the self-catalytic effect is carried out continuously in the seam, which causes the metal to corrode seriously.In this paper, three representative acidic, alkaline and neutral soil simulated solutions in Yingtan, Xinjiang, and Yimeng, Inner Mongolia were selected as corrosion medium.The crevice corrosion behavior of X100 pipeline steel in simulated gap device was studied, and the effect of applied current cathodic protection on gap corrosion was studied, and the crevice corrosion law of X100 pipeline steel in acid-base neutral soil simulation environment was explored.The crevice corrosion behavior of X100 pipeline steel in simulated soil solution of Yingtan, Xinjiang and Inner Mongolia was studied.The experimental results show that the Cl-concentration of the solution in the soil of Yingtan, Korla and Yimeng increases with the prolongation of time, and the Cl-concentration increases rapidly in the initial stage of soaking.After soaking for more than 20 hours, the increase of Cl-concentration was slow. X100 pipeline steel in Yingtan soil simulation solution, Korla soil simulation solution, Yimeng soil simulation solution medium, with the prolongation of soaking time.The electrode potential E at each position in the seam decreased to different degrees, and the electrode potential E gradually decreased from the seam opening to the seam bottom, which indicated that the corrosion at the bottom of the joint was the most serious.The cathodic polarization characteristics of X100 pipeline steel in the gap are experimentally studied. The influence of polarization time, cathode polarization control potential and different media on the polarization potential in the gap are studied.The degree of crevice corrosion of X100 pipeline steel under three kinds of media under cathodic protection was analyzed.The results show that in the soil simulated solution medium of Yingtan, Korla and Yimeng, the polarization voltage of -1000mVCS enters through the seams of the WX100 pipeline steel, and the polarization potential at each position in the seam decreases with the prolongation of the polarization time.At the same polarization time, the polarization potential from the seam to the bottom of the seam increases with the prolongation of the polarization time, and the gradient of the polarization potential from the seam to the bottom of the seam is less obvious than that of the simulated slit specimen of the X100 pipeline steel in Yingtan, Korla.In the soil simulated solution medium, with the decrease of the control potential at the seams, the polarization potential at all positions in the seam showed a negative gradient, and when the polarization potential was -1000mVCSE-1150mVCSE,The polarization electrode at every position in the seam is below the critical protection voltage, and the cathodic protection effect is achieved, and when the slit voltage is -850mVCSE, the depth of the slit bottom is in the underprotected state in the simulated solution medium of Yingtan soil.
【学位授予单位】：内蒙古科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1

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