供水系统铸铁管材的腐蚀行为及影响因素研究

发布时间：2018-01-09 18:33

本文关键词：供水系统铸铁管材的腐蚀行为及影响因素研究　出处：《哈尔滨工业大学》2014年博士论文　论文类型：学位论文

【摘要】：本课题以保证供水管网的水质安全为目的,通过静态实验和动态实验较为全面地探讨了铸铁管材的腐蚀机理及影响因素。从管段中提取生长环及污泥,经分离提纯得到硫酸盐还原菌和铁细菌菌株,以相应的培养基培育菌株作为腐蚀介质,监测微生物的生长代谢对生长环境的影响。采用电化学方法和表面分析技术研究硫酸盐还原菌和铁细菌对金属管道腐蚀的影响,探讨微生物存在时,阳极金属的活性溶解和生物膜下点蚀的萌发和生长发展。通过动态实验模拟水流对管壁的冲刷作用,研究不同流速、流态下管材腐蚀行为的变化。实验发现,管网中微生物主要存在于管道内壁,而金属表面的粗糙程度与细菌的黏附和生物膜的形成等因素有关,因此细菌总数、铁细菌和SRB数量在铸铁管材上都呈现出最大值(分别为5.3×107 cfu/cm2、2.5×105 cfu/cm2、184cfu/cm2,t=45d),说明管材的选择对水中细菌总数和生长环的形成是至关重要的。硫酸盐还原菌可使铸铁管材发生点蚀现象。但相对于无菌水,腐蚀产物层的结构更加多样复杂,呈现不均匀性。本文针对供水管网的运行情况特点,揭示了水流速度和与铸铁管材腐蚀速率的关系。腐蚀速率与主体水流速线性相关,流速的增加,加快了水中腐蚀性物质的传输速率和电荷转移过程,从而促进铸铁的腐蚀进程。动态实验中维持一定的水力停留时间可导致铸铁管材的腐蚀速率增大,说明主体水由静态-动态或动态-静态的变化促进了铸铁管材的腐蚀过程。流速的变化加快了使腐蚀性物质的传输和腐蚀进程,从而使管材的腐蚀速率大于主体水流速恒定的状态。此外,铸铁管材的腐蚀与水质条件变化密切相关。随着腐蚀速率的增加,水中浊度和色度明显增加,说明铸铁管材腐蚀是“有色水”的产生的主要原因;此外,腐蚀还可能导致铸铁管材向主体水中释放铁离子,使水中Fe2+浓度和总铁含量增大,影响供水水质。本研究建立了水中氯浓度与铸铁管材腐蚀速率的变化关系。Cl-可使铸铁表面表面活性点增多,吸附的Cl-含量增大,而电荷转移电阻Rct降低至6307×103Ω·cm2(CCl-=2.0mg/L),从而加速了铁的阳极活性溶解过程,使铸铁管材的腐蚀速率增大。通过SEM观察到铸铁表面存在明显的点蚀坑,且蚀孔深度与铸铁表面的平均粗糙度随时间的增加而增大,表明水中氯离子的存在可导致铸铁管材的腐蚀过程以点蚀的形式向管壁内部发展,对管材的破坏性极大。研究表明水中氯离子作用下生成的腐蚀产物主要为Fe2O3、Fe3O4和α-Fe OOH和γ-Fe OOH,其结构疏松多孔。氯离子存在时,易形成稳定性较差的β-Fe OOH,暴露于空气中转化为α-Fe OOH和γ-Fe OOH,因此在XRD分析中并未检测到此相。但β-Fe OOH大量存在于腐蚀产物层内部,其相针之间的间隙较大,可以使水分存留其中,为点蚀的发生创造有利条件。与α-Fe OOH相比,其结构比较疏松,不易于形成致密的钝化层而抑制管道的腐蚀发生,而Cl-可能阻止腐蚀产物向较稳定的α-Fe OOH转变,抑制管材表面钝化层的形成。
[Abstract]:This issue in order to ensure the quality and safety of the water supply network for the purpose of through static and dynamic experiments of a more comprehensive study on the factors of corrosion mechanism of cast iron pipe and influence. The extraction of growth ring and sludge from the pipe, after separation and purification by sulfate reducing bacteria and iron bacteria strains, with the corresponding culture medium cultivation strains as corrosion medium that affected the growth and metabolism of microorganisms on the growth environment monitoring. Affected by electrochemical methods and surface analysis techniques of sulfate reducing bacteria and iron bacteria on the corrosion of metal pipes, to investigate the microbial existence, pitting germination and growth development of anode metal dissolution and biofilm. Through the experiment of simulating water flow to scour pipe on the wall, different flow rate, change of corrosion behavior of tubing flow. It was found that the main microbial network in the inner wall of the pipeline, and the metal surface The roughness and bacterial adhesion and biofilm formation and other factors, so the number of total bacteria, iron bacteria and SRB in the cast iron pipe takes on a maximum value (5.3 x 107 cfu/cm2,2.5 x 105 cfu/cm2184cfu/cm2, t=45d), description of material selection for the total number of bacteria in water and growth is essential for the formation of the ring the sulfate reducing bacteria. The cast iron pipe pitting phenomenon. But compared with sterile water, the structure of the corrosion product layer is more complex, appear uneven. The operation according to the characteristics of the water supply network reveals the flow velocity and rate of cast iron pipe corrosion. The corrosion rate and the main flow velocity, linear correlation, velocity the increase of the transmission rate and accelerate the charge transfer process of corrosive substances in water, so as to promote the process of iron corrosion. Maintain a certain hydraulic residence time in dynamic experiment The corrosion rate of cast iron pipe can lead to the increase of main water change from static and dynamic - static or dynamic promoted the corrosion process of cast iron pipe. The change of flow rate to speed up the transmission and corrosion process of corrosive substances, so that the corrosion rate is greater than the main flow velocity constant. In addition, the change of corrosion and the water quality conditions of cast iron pipe is closely related. With the increase of corrosion rate, color and turbidity of water increased significantly, that cast iron pipe corrosion is the main reason of colored water produced; in addition, may also lead to corrosion of cast iron pipe release iron to the main body of water, the concentration of Fe2+ in water and the total iron content increases, affecting water quality. This study established the.Cl- relationship of chloride concentration and corrosion rate of cast iron pipe can make the surface of cast iron surface active point increase, increasing the content of Cl- adsorption, and charge transfer Shift resistor Rct is reduced to 6307 x 103. Cm2 (CCl-=2.0mg/L), which accelerated the anodic dissolution process of iron, the corrosion rate of cast iron pipe increases. Observed by SEM has obvious pitting surface of cast iron and cast iron, pitting depth and surface roughness average time increases, that the presence of chloride ions in the water can lead to corrosion of cast iron pipe to pipe wall to form the internal development of pitting, damage to pipe greatly. The results show that the corrosion products under the effect of chloride ions in the water are mainly Fe2O3, Fe3O4 and -Fe OOH -Fe OOH alpha and gamma, the porous structure. The presence of chloride ions. Easy to form the poor stability of beta -Fe OOH, exposed to the air into a -Fe OOH and gamma -Fe OOH, so the XRD analysis did not detect this phase. But there are a lot of OOH beta -Fe in the corrosion product layer, a gap between the needle Big, can make the water retention, create favorable conditions for the occurrence of pitting. Compared with a -Fe OOH, the structure is loose, corrosion is not easy to form a compact passivation layer and inhibit the pipeline, while the Cl- may prevent the corrosion product transition to more stable alpha -Fe OOH, inhibit the formation of tube surface passivation layer.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU991.38

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