1、循环冷却水中微生物对金属腐蚀的研究Research on Metal Corrosion by Microorganisms In Circulating Cooling Water学科专业：环境工程研 究 生：指导教师：二零xx年十二月摘 要工业循环冷却水用水量巨大，采用再生水代替地表水作为补充水源，可有效节水，然而由于再生水水质的影响，微生物产生的腐蚀、黏泥问题较为严峻。金属腐蚀的本质是电化学反应，为了获取硫酸盐还原菌（Sulfate-Reducing Bacteria，SRB）和铁细菌（Iron-Oxidizing Bacteria，IOB）对Q235碳钢腐蚀电化学行为、碳钢挂片表面形貌
2、以及元素成分的影响，提供解释微生物腐蚀机理的数据，采用实验方法展开相关研究。通过运行循环冷却水动态模拟装置，获取循环冷却水，经富集、分离、纯化得到硫酸盐还原菌、铁细菌。分别研究了它们的生长特性，并利用CS2350电化学工作站，研究了它们对Q235碳钢腐蚀的自腐蚀电位（开路电位）、极化电阻、腐蚀率等电化学指标的影响；应用环境扫面电子显微镜（Environmental Scanning Electron Microscope，ESEM）研究了微生物作用下碳钢腐蚀挂片的表面形貌、采用X射线能量色散谱方法（X-ray Energy Dispersive Spectroscopy，EDS）研究了挂片元素
3、成分变化。电化学实验表明，SRB、IOB均能显著降低培养液的自腐蚀电位，增大腐蚀反应动力。与未接种的电解池相比，在促进腐蚀最显著的阶段，SRB能使腐蚀率达到未接种的3.17倍，IOB能使腐蚀率达到未接种的1.53倍。在极化电阻、腐蚀率达到稳定以后，两种菌仍能显著降低培养液的极化电阻，增加腐蚀率，其中SRB能使腐蚀率升高62%左右，而IOB能使腐蚀率升高29%左右。极化曲线表明，SRB能改变电化学反映动力学参数a、c，显著影响阴极反应。交流阻抗谱的测定结果与极化电阻曲线反映的现象一致。直接观察碳钢挂片可以看出，SRB能使挂片表面颜色变黑，形成凸起；而IOB能使挂片表面形成点蚀坑。ESEM观察表明
4、，两种菌都能显著改变碳钢表面形貌，形成特殊结构。EDS元素分析表明，SRB能使O、P元素含量显著提高，使Fe、S含量降低；IOB能使O、P、K等元素含量均增加，C、Fe等元素含量减少。综上，SRB与IOB能显著影响Q235碳钢的电化学行为、碳钢挂片表面形貌与元素成分比例，从而促进碳钢腐蚀。关键词：循环冷却水；微生物腐蚀；电化学；表面形貌ABSTRACTAs is known to us, it is an effective solution to replace surface water with reclaimed water as the make-up water in the in
5、dustrial circulating cooling water system, since the water consumption of those systems is enormous. However the problem of Microbial Inuenced Corrosion (MIC) and microbial slime would be much more serious, considering the influence of the water quality of reclaimed water. It is widely convinced tha
6、t the nature of metal corrosion is electrochemical reaction, so some related experimental methods were adopted to achieve these research purposes: obtaining the way how sulfate-reducing bacteria(SRB) and iron-oxidizing bacteria(IOB) influence the electrochemical behavior，surface morphology and surfa
7、ce chemical element of Q235 carbon steel, supplying data support for explaining the mechanism of MIC.SRB and IOB were achieved by enriching, separating, purifying from circulating cooling water generated by operating the dynamic analog device. After that the growth characteristics of those bacteria
8、were researched. Then the influence of some electrochemical indexes such as open circuit potential (OCP), polarization resistance and corrosion rate were researched with the application of CS2350 electrochemical workstation. Besides, the changes of surface morphology of carbon steel coupons affected
9、 by microbe were researched by observing with the Environmental Scanning Electron Microscope (ESEM) and the surface chemical element changes of those carbon steel coupons were analyzed by the method of X-ray Energy Diffraction Spectrum (EDS).The results of electrochemical experiments showed that SRB
10、 and IOB could considerably decrease the OCP so as to increase the corrosion reaction kinetics. SRB could increase the corrosion rate of the medium up to 3.17 times, and IOB could increase the corrosion rate of the medium up to 1.53 times compared with the medium without inoculating microorganism. A
11、fter the polarization resistance and corrosion rate reached the stable stage, the corrosion rate could be separately increased by approximately 62% and 29% at the effect of SRB and IOB. The polarization curve manifested that SRB and IOB may change the electrochemical kinetics parameters such as a、c，
12、especially affect the cathodic reaction. The phenomenon reflected by Electrochemical Impedance Spectroscopy (EIS) coincided well with that by polarization resistance.The direct observation of carbon steel coupons indicated that, SRB could turn the surface color into black and generate some protubera
13、nces while IOB could cause corrosion pit. The observation with ESEM demonstrated that both the two kinds of bacteria could remarkably change the surface morphology of carbon steel and form special structures. The analysis of chemical element showed that SRB could increase the percentage of oxygen an
14、d phosphorus remarkably, and decrease the percentage of iron and sulphur slimly. At the same time, IOB could also increase the percentage of oxygen, phosphorus, and potassium considerably, and decrease the percentage of carbon and iron at certain degree. In one word, SRB and IOB could apparently aff
15、ect the electrochemical behavior, surface morphology and chemical element proportion of Q235 carbon steel so as to promote its corrosion.KEY WORDS：Circulating Cooling Water, Microorganism Influenced Corrosion, Electrical Chemical, Surface Morphology目 录第一章绪论11.1 研究背景11.1.1 循环冷却水系统简介11.1.2 再生水的循环利用21.
16、1.3 循环冷却水系统的微生物问题21.1.4 硫酸盐还原菌和铁细菌的主要特性41.1.5 金属腐蚀理论基础61.2 国内外研究现状81.2.1 微生物腐蚀机理的概述81.2.2 典型微生物腐蚀机理91.2.3 几种金属的微生物腐蚀机理121.3 研究内容与意义131.3.1 技术路线131.3.2 主要研究内容141.3.3 研究目的与意义15第二章微生物腐蚀研究方法与材料162.1 获取循环冷却水的方法162.2 微生物的富集、分离与纯化方法162.2.1 SRB的富集、分离与纯化162.2.2 IOB的富集、分离与纯化192.3 电化学实验材料与制作处理方法202.3.1 电化学实验材料202.3.2 制作与处理方法222.4 金属腐蚀的表面分析方法23
