剥离涂层下微生物对金属腐蚀影响的研究

发布时间：2018-04-21 15:49

本文选题：SRB + 丝束电极　；参考：《中国民航大学》2017年硕士论文

【摘要】：硫酸盐还原菌(SRB)是造成埋地金属管道腐蚀的主要因素之一,对于剥离涂层下金属管道而言,防腐层与管道之间形成的缝隙环境更有利于SRB的生存,从而破坏金属管道的防腐层性能,并影响金属基体的腐蚀行为,不仅造成严重了的经济损失,而且大大降低了油气输送的安全性。本文采用自制装置通过失重法探究SRB在不同剥离缝隙厚度下对剥离涂层下X80钢、Q235钢腐蚀行为的影响。在失重法研究结果基础上,采用丝束电极实验装置以及微电极离子传感器,通过测试电极电化学参数同时检测缝下溶液pH值与Cl-浓度变化规律,深入研究SRB对剥离涂层下金属腐蚀行为的影响。研究结果表明:(1)由失重法可得,无SRB的自然腐蚀条件下,剥离涂层下X80钢耐腐蚀性强于Q235钢;而有SRB时,剥离涂层下Q235钢耐腐蚀性强于X80钢;剥离缝隙厚度对Q235钢的腐蚀影响大于X80钢。(2)对于剥离涂层下X80钢而言,有SRB条件下,SRB参与电极阴极还原过程,消耗缝下溶液中的H+,一定程度上抑制溶液酸化,使得缝隙腐蚀诱发阶段为0~18h,比无SRB存在时延长12h;随着浸泡时间推移,缝隙腐蚀沿缝隙纵深方向扩张,SRB代谢产物堆积使得缝口持续堵塞,缝隙腐蚀加剧期也比无SRB时延长;浸泡11d后缝下电极腐蚀开始减缓,浸泡15d后缝口传质障碍消除缝隙腐蚀进入稳定期,都比无SRB条件下时间延后了。(3)对于剥离涂层下Q235钢而言,无论溶液环境中有无SRB,在剥离厚度相同时,随着剥离深度的增大,缝下金属电极的腐蚀速度均逐渐减弱;对比Q235钢在不同剥离缝隙厚度下的腐蚀行为,当厚度为0.5mm时缝下金属电极腐蚀程度最为严重。随着剥离缝隙厚度的增大,SRB对缝下金属电极的腐蚀影响增大,缝下金属电极的腐蚀由缝隙边缘逐渐扩展到缝隙底部。综上,对于剥离涂层下缝内金属腐蚀,由于SRB参与电极腐蚀反应,活化电极表层金属,增大了缝下电极的腐蚀速率和腐蚀程度,同时使得缝下电极腐蚀区域进一步扩大,减小了缝隙内外电极腐蚀差异性,故有SRB条件下腐蚀更为严重。
[Abstract]:Sulfate-reducing bacteria (SRB) is one of the main factors causing corrosion of buried metal pipelines. For metal pipelines with peeling coating, the gap environment between anticorrosive coating and pipeline is more favorable to the survival of SRB. Thus the corrosion resistance of metal pipeline is destroyed and the corrosion behavior of metal substrate is affected which not only results in serious economic loss but also reduces the safety of oil and gas transportation. In this paper, the effect of SRB on corrosion behavior of X80 steel Q235 steel under peeling coating was investigated by means of weightlessness method. Based on the results of weightlessness method, the changes of pH value and Cl- concentration in solution under slit were measured by using a wire beam electrode experimental device and a microelectrode ion sensor, and the electrochemical parameters of the electrode were measured simultaneously. The effect of SRB on the corrosion behavior of metals under peeling coating was studied. The results show that the corrosion resistance of X80 steel is stronger than that of Q235 steel under the condition of natural corrosion without SRB, and the corrosion resistance of Q235 steel with SRB is stronger than that of X80 steel with SRB. The effect of delamination gap thickness on corrosion of Q235 steel is greater than that of X80 steel. The crevice corrosion induced stage was 0 ~ 18h, which was 12 hours longer than that without SRB, and the gap corrosion extended along the crevice depth along the crevice depth to make the gap continue to block, and the crevice corrosion exacerbation period was longer than that without SRB. After soaking for 11 days, the corrosion of the electrode began to slow down. After soaking for 15 days, the mass transfer barrier of the seam mouth to eliminate the gap corrosion entered into the stable period, which was delayed by the time of the Q235 steel under the condition of no SRB. With or without SRB in solution environment, the corrosion rate of metal electrode decreases with the increase of stripping depth, and the corrosion behavior of Q235 steel is compared with that of Q235 steel under different delamination thickness. When the thickness of the metal electrode is 0.5mm, the corrosion degree of the metal electrode is the most serious. The effect of SRB on the corrosion of the metal electrode was increased with the increase of the thickness of the strip gap, and the corrosion of the metal electrode under the seam gradually extended from the edge of the slot to the bottom of the slot. In conclusion, for the metal corrosion under the slit of peeling coating, the corrosion rate and corrosion degree of the electrode are increased because SRB participates in the electrode corrosion reaction, which increases the corrosion rate and corrosion degree of the electrode, and further expands the corrosion area of the electrode under the seam. The corrosion difference between the inner and outer electrodes is reduced, so the corrosion is more serious under the condition of SRB.
【学位授予单位】：中国民航大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE988.2

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