硫酸盐还原菌对X80管线钢在土壤环境中腐蚀行为的影响

发布时间：2018-05-19 11:56

本文选题：X80管线钢 + 土壤环境　；参考：《中国石油大学(华东)》2015年博士论文

【摘要】：在土壤环境中,微生物腐蚀是管线钢腐蚀行为的主要影响因素之一。其中厌氧的硫酸盐还原菌(SRB)对埋地管线钢的腐蚀影响最为显著。目前,高强度的X80管线钢已经成为石油天然气输送领域的首选用钢,由于大量管线钢埋于地下,使其发生腐蚀机率增加,势必会引起腐蚀现象,严重威胁了埋地管线的安全运行。特别是在含有SRB的土壤环境中X80管线钢发生应力腐蚀开裂(SCC)行为的可能性大大增加。因此,非常有必要研究土壤环境中的活性SRB对X80管线钢腐蚀行为的影响规律以及在含SRB土壤中金属发生SCC行为的腐蚀机制。本文从鹰潭、沈阳、大港三种实际土壤中富集培养、分离纯化SRB菌种,并绘制出了三种土壤环境中的SRB生长曲线,利用生物显微镜观察SRB附着形貌,并对SRB的生长过程及其对周围环境腐蚀因子的影响进行研究。结果表明:SRB归为脱硫弧菌属,为革兰氏阴性菌;土壤环境中活性SRB数量与H2S、SO42-等腐蚀环境因子有一定的对应关系。采用扫描电子显微镜(SEM)、能谱仪(EDS)及电化学阻抗谱技术(EIS)研究了硫酸盐还原菌(SRB)在沈阳土壤中不同生长阶段的膜层对X80钢腐蚀行为的影响规律。结果表明,当浸泡初期时,试样电极表面以SRB生物膜吸附为主,此时生物膜能够减缓X80钢腐蚀反应的进行。随着浸泡时间的增加,电极表面有少量生物膜和腐蚀产物膜共存,腐蚀产物膜的生成破坏了原有生物膜的保护作用,导致金属腐蚀加剧。当试样浸泡240h时,试样表面形成致密的腐蚀产物膜,抑制了腐蚀反应的进行,此时腐蚀产物膜对X80钢的保护作用远大于生物膜。采用动电位扫描技术、交流阻抗技术、慢应变速率拉伸试验研究了SRB浓度对X80钢腐蚀行为的影响,并利用扫描电镜(SEM)对试样断口形貌进行表征。结果表明:活性SRB浓度越大,金属腐蚀行为越严重。SRB能够促进点蚀现象的发生。当有应力共同作用时,SRB对金属应力腐蚀开裂行为起到了促进作用。通过自制恒温应力加载电化学测量装置‖,利用交流阻抗技术和SSRT试验,研究了SRB与应力共同作用下外加电位对X80钢应力腐蚀开裂行为的影响,并结合扫描电镜(SEM)对试样断口形貌进行表征。结果表明:-850mV电位下金属处于一定的阴极保护状态。在自腐蚀电位和-650mV电位下,SRB起到促进试样点蚀坑的形成的作用,金属应力腐蚀开裂机理为阳极溶解机制。-1200mV电位下,由于SRB的存在,加剧了氢向金属内部扩散作用,材料应力腐蚀开裂机理为氢致开裂机制。采用Devanathan-Stachurski双电解池氢渗透技术和扫描电镜SEM分析,研究了SRB对X80钢在鹰潭土壤模拟溶液中氢渗透行为的影响。结果表明:X80钢在接菌土壤模拟溶液中的氢渗透电流密度是灭菌土壤条件下的3-4倍。阴极极化电位能加剧X80钢在含SRB土壤模拟溶液中的氢渗透行为。
[Abstract]:Microbial corrosion is one of the main factors affecting corrosion behavior of pipeline steel in soil environment. The corrosion of buried pipeline steel was affected most obviously by anaerobic sulfate reducing bacteria SRB. At present, the X80 pipeline steel with high strength has become the preferred steel in the field of petroleum and natural gas transportation. Because a large number of pipeline steels are buried underground, the probability of corrosion will increase, which will inevitably lead to corrosion. It is a serious threat to the safe operation of buried pipelines. Especially in the soil environment containing SRB, the possibility of stress corrosion cracking (SCC) behavior of X80 pipeline steel is greatly increased. Therefore, it is necessary to study the effect of active SRB in soil environment on the corrosion behavior of X80 pipeline steel and the corrosion mechanism of metals in SRB containing soils. In this paper, SRB strains were isolated and purified from three kinds of real soils of Yingtan, Shenyang and Dagang. The SRB growth curves in three soil environments were plotted, and the morphology of SRB attachment was observed by biomicroscopy. The growth process of SRB and its influence on environmental corrosion factor were studied. The results showed that the SRB was classified as Vibrio desulphurization and Gram-negative bacteria, and the amount of active SRB in soil environment was related to corrosion environmental factors such as H _ 2S _ 2SO _ 4 _ 4-. The effect of sulfate reducing bacteria SRB on corrosion behavior of X80 steel in Shenyang soil was studied by means of scanning electron microscope (SEM), energy spectrometer (EDS) and electrochemical impedance spectroscopy (EIS). The results show that SRB biofilm is the main adsorbent on the electrode surface at the initial stage of soaking, and the biofilm can slow down the corrosion reaction of X80 steel. With the increase of immersion time, a small amount of biofilm and corrosion product film co-exist on the electrode surface. The formation of corrosion product film destroys the protective effect of the original biofilm, which leads to the deterioration of metal corrosion. When the sample was soaked for 240 h, a dense corrosion product film was formed on the surface of the sample, which inhibited the corrosion reaction. At this time, the protective effect of the corrosion product film on X80 steel was much greater than that on the biofilm. The effect of SRB concentration on corrosion behavior of X80 steel was studied by potentiodynamic scanning technique, AC impedance technique and slow strain rate tensile test. The fracture morphology of X80 steel was characterized by scanning electron microscope (SEM). The results show that the higher the concentration of active SRB is, the more serious the corrosion behavior of metal is. SRB can promote the occurrence of pitting corrosion. The SRB can promote the stress corrosion cracking behavior of metals when there is stress interaction. The effect of applied potential on stress corrosion cracking behavior of X80 steel under the combined action of SRB and stress was studied by means of AC impedance technique and SSRT test. The fracture morphology was characterized by scanning electron microscope (SEM). The results show that the metal is in a certain cathodic protection state at the potential of:-850 MV. At self-corrosion potential and -650mV potential, SRB plays an important role in promoting the formation of pitting pits. The mechanism of metal stress corrosion cracking is anodic dissolution mechanism .-1200mV potential. Due to the existence of SRB, the diffusion of hydrogen into metal is aggravated. The mechanism of stress corrosion cracking is hydrogen induced cracking. The effect of SRB on hydrogen permeation behavior of X80 steel in Yingtan soil simulated solution was studied by means of Devanathan-Stachurski double electrolytic cell hydrogen permeation technique and scanning electron microscope (SEM) analysis. The results showed that the hydrogen permeation current density in the inoculated soil simulated solution was 3-4 times higher than that in sterilized soil. The cathodic polarization potential can increase the hydrogen permeation behavior of X80 steel in simulated solution containing SRB.
【学位授予单位】：中国石油大学(华东)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE988.2

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