Institutional Repository of Key Laboratory of Marine Environmental Corrosion and Bio-fouling, IOCAS
|Place of Conferral||中国科学院海洋研究所|
|Keyword||微生物腐蚀 Microbiologically influenced corrosion (MIC) 铁还原菌Halomonas titanicae Iron-reducing bacteria (Halomonas titanicae) 电子受体 Electron acceptor 合金元素 Alloying element 2205双相不锈钢 2205 duplex stainless steel|
微生物腐蚀（MIC）是影响海洋工程金属材料如钢铁等服役期安全性的因素之一，其对工程设施直接或间接造成的损害给人类社会带来巨大的经济损失、人身威胁和环境破坏。铁还原菌IRB是一类可以将固态的Fe(III)异化还原为离子态Fe(Ⅱ)的微生物，在铁循环过程中发挥着重要的作用。但其对材料尤其是铁基金属材料的腐蚀机制存在争议。造成争议的原因很多，从微生物代谢过程的角度考虑可能与电子受体的选择有关。同时，合金化作为提高金属材料耐蚀性和抗菌性的重要手段之一，合金元素对IRB的抗菌性能却鲜有报道。本文选取分离自汇泉湾的兼性厌氧IRB菌株H. titanicae，围绕其不同环境中电子受体的选择差异，研究了其在有氧/无氧条件下电子受体的选择不同对海洋环境典型金属材料合金钢和不锈钢腐蚀行为的影响，并解析其不同的腐蚀机制。同时，对比了Cu和Ni等合金元素在抑制H. titanicae所致金属材料腐蚀方面的作用，并提出相应的腐蚀抑制机制。主要研究结果如下：
（1）揭示了H. titanicae对EH40钢腐蚀影响的电子受体依赖性。研究了不同溶解氧浓度下H. titanicae对EH40钢腐蚀的影响，发现有氧/无氧环境下，H. titanicae的腐蚀影响不同。有氧环境中，H. titanicae趋向于有氧呼吸，选择O2作为电子受体，导致体系中DO值降低，抑制了阴极氧还原反应，从而抑制了EH40钢的腐蚀。而在无氧环境中，H. titanicae利用Fe(III)作为电子受体，使得固态的Fe(III)转化为离子态的Fe2+，暴露了新鲜表面从而提供了更多的活性位点，同时阻碍了疏松的Fe(III)产物膜向更致密的Fe3O4的转化，破坏了产物膜的保护性。此外，无氧环境中生物膜下H. titanicae可能以H2为电子供体引起膜下腐蚀，从而促进EH40钢的腐蚀。
（2）探究了Cu和Ni合金元素在H. titanicae以Fe(III)为电子受体所致合金钢腐蚀方面的抑制作用。选取了不同Cu、Ni含量的回火索氏体合金钢，研究了其在无氧环境H. titanicae作用下的腐蚀，发现合金元素Cu的添加和Ni含量的均提高了对无氧环境下H. titanicae所致合金钢腐蚀有抑制作用，且含量为1.3%的Cu添加缓蚀作用强于将Ni含量从4.8%提高至7.2%。Cu添加和提高Ni含量的腐蚀抑制作用是由于附着细菌的减少，从而减少细菌从Fe(III)向Fe(Ⅱ)的异化还原作用，但两种合金元素表现出不同的抑制机制。1.3Cu3.3Ni-HSLA钢通过释放Cu离子，对H. titanicae有一定的杀菌作用，减少附着细菌数量；而7.2Ni-HSLA钢对附着细菌没有明显的杀菌作用，是通过增加含Ni化合物的生成如NiFe2O4抑制细菌的附着，从而抑制H. titanicae对钢的腐蚀作用。
（3）研究了H. titanicae对钝性金属不锈钢腐蚀影响的电子受体的依赖性。选取了2205 DSS，探究其在不同溶解氧环境下的腐蚀行为。结果表明，与EH40钢不同，H. titanicae在有氧/无氧环境中电子受体的选择不同均加速了2205 DSS的腐蚀。有氧环境中，H. titanicae选择O2作为电子受体，导致DO值降低，一方面海水中腐蚀性离子如Cl-引发2205 DSS点蚀，破坏了钝化膜，而在O2浓度低的情况下不能及时修复，导致点蚀进一步加深；另一方面，H. titanicae在样品表面的附着形成局部氧浓差电池，造成生物膜下局部腐蚀，促进了点蚀的发展。无氧环境中，H. titanicae利用Fe(III)作为电子受体，破坏了钝化膜的完整性，而由于缺乏O2，导致被破坏的钝化膜得不到修复，使得腐蚀性离子如Cl-深入到点蚀坑内部，促进了点蚀的发展。
（4）初步探究了Cu合金元素添加对2205 DSS耐H. titanicae腐蚀影响机制。选取了Cu元素百分含量为2.27 %的2205Cu DSS，研究了其在有氧/无氧环境中对H. titanicae所致2205 DSS腐蚀的抑制作用。结果表明，有氧环境下，Cu添加在一定程度上反而降低了2205 DSS在无菌/有菌体系中的耐蚀性，原因是O2的存在使得2205Cu DSS中的Cu发生阳极溶解反应，以离子形态溶解到体系中，破坏了表面钝化膜的完整性，同时H. titanicae以O2为电子受体的代谢过程消耗了O2，降低了溶解氧浓度，对不锈钢钝化膜的修复造成不利影响，导致2205Cu DSS在有氧环境的点蚀深度大于2205 DSS。而在无氧环境下，2205Cu DSS中Cu离子释放起到一定的杀菌作用，减少了H. titanicae以Fe(III)为电子受体的代谢活动，从而减少了细菌对钝化膜的破坏，抑制了不锈钢的点蚀深度。
本文从电子受体角度解释了IRB腐蚀机制存在争议的原因，并揭示了H. titanicae在有氧/无氧环境下电子受体的依赖性对金属材料腐蚀的影响与材料表面特性的关联。同时，首次研究并比较了Cu、Ni合金元素在抑制H. titanicae作用下金属材料腐蚀的作用，分别讨论了腐蚀抑制机制。因此，本文对完善海洋环境MIC理论和抗菌材料的研究具有一定的理论指导意义。
Microbiologically influenced corrosion (MIC) is one of the factors that affect the safety of marine engineering metal materials such as steels during the service period. Damages to the equipment induced by bacterial cause huge economic losses, personal threats and environmental pressures. Iron-reducing bacteria (IRB) can reduce solid Fe(Ⅲ) to dissoluble Fe(Ⅱ), which plays an important role in the iron cycle. However, summarizing the existing research results, the influence of IRB on corrosion of metal materials is controversial, and there are many factors to be responsible for the conflict in corrosion affected by IRB. From the perspective of microbial metabolism, it may be related to the choice of electron acceptors. At the same time, alloying is one of the important means to improve the antibacterial property of metallic materials, but the effects of alloying elements on IRB are rarely reported. In this paper, focusing on the utilization of electron acceptor, a facultative anaerobic IRB (Halomonas titanicae, H. titanicae), isolated from Huiquan Bay, was selected to explore the effect on corrosion of typical metal materials in the marine environment including alloy steels and stainless steels in base of different choices of electron acceptors in different dissolved oxygen environments. And according to the experimental results, the different corrosion mechanisms were explained. In the meantime, the effect of alloying elements Cu and Ni in inhibiting the corrosion of metal materials caused by H. titanicae was explored and compared, and the mechanisms of H. titanicae on corrosion of different metal materials was discussed. The specific research contents are as follows:
(1) The electron acceptor dependence of H. titanicae on corrosion of EH40 steel was revealed. The effects of H. titanicae on corrosion of EH40 steel under different dissolved oxygen concentrations was studied, and it was found that the influences of H. titanicae is different under aerobic and anaerobic environments. In the aerobic system, H. titanicae selected O2 as electron acceptor resulting in the decreased dissolved oxygen concentration, which inhibited corrosion of EH40 steel via weakening cathodic oxygen reduction reaction. But in the anaerobic system, H. titanicae utilized Fe(III) as electron acceptor, so that solid Fe(III) was converted to ionic Fe2+, exposing more fresh surface. And the conversion of the loose Fe(III) corrosion product films to the dense Fe3O4 film reduced. Hence, the protective properties of the product films were destroyed, providing more active sites. At the same time, H. titanicae under the biofilm might use H2 as the electron donor to cause corrosion, thereby promoting the corrosion of EH40 steel.
(2) The inhibitory effect of Cu and Ni alloying elements on corrosion of alloy steel caused by H. titanicae with Fe(III) as the electron acceptor was explored. The tempered sorbite alloy steels with different contents of Cu and Ni were selected, and the corrosion behaviors under the action of H. titanicae using Fe(III) in the anaerobic environment was studied. It was found that the Cu addition and high-content of Ni both have inhibitory effect on corrosion caused by H. titanicae, and the inhibitory effect of 1.3% Cu was stronger than that of increasing the content of Ni from 4.8% to 7.2%. The corrosion inhibitions by adding Cu and increasing content of Ni were due to the reduction of bacterial cells in the biofilm, thereby reducing the dissimilatory reduction of H. titanicae from Fe(III) to Fe(II), but the mechanisms were different from each other. 1.3Cu3.3Ni-HSLA had a certain sterilization effect on H. titanicae by releasing copper ions and reduced the number of attached bacteria; while 7.2Ni-HSLA steel had no obvious sterilization effect on attached bacteria, and it inhibited the attachment of bacteria through formatting more Ni-containing compounds such as NiFe2O4.
(3) The electron acceptor dependence of H. titanicae on corrosion of passive metallic stainless steel was studied. The 2205 DSS was selected to explore its corrosion behaviour in different dissolved oxygen environments. The results showed that the different choices of electron acceptors of H. titanicae in different dissolved oxygen concentrations all accelerated the corrosion of 2205 DSS, which was different from EH40 steel. In the aerobic environment, H. titanicae selected O2 as electron acceptor, which leaded to a decrease in dissolved oxygen concentration. On the one hand, corrosive ions in seawater such as Cl- triggered pitting corrosion of 2205 DSS, destroying the passivation film. It could not be repaired timely in the case of low O2 concentration, resulting in further deepening of pitting corrosion. On the other hand, the attachment of H. titanicae on the sample surface formed a local oxygen concentration cell, which caused local corrosion under the biofilm and promoted the development of pitting corrosion. In the anaerobic environment, H. titanicae used Fe(III) as electron acceptor, which destroyed the protectivity of the passivation film. Due to the lack of O2, the damaged passivation film could not be repaired, causing corrosive ions such as Cl- to deepen to a point. Thus, it enhanced the development of pitting corrosion.
(4) The resistance to H. titanicae of Cu-bearing 2205 DSS was explored utilized one kind of 2205Cu DSS (2.27% Cu content). The inhibitory effects on corrosion of 2205Cu DSS induced by H. titanicae in different dissolved oxygen environments were studied. Under the aerobic condition, the addition of Cu reduced the corrosion resistance of 2205 DSS in a sterile/ biotic system. The presence of O2 made the Cu atoms in 2205Cu DSS underwent an anodic dissolution reaction and dissolved into the system. Hence, the passive film on the surface of the stainless steel was destroyed, and the metabolic process of H. titanicae using O2 as the electron acceptor consumed O2 and reduced the dissolved oxygen concentration, which adversely affected the repair of the passive film, resulting in deeper pitting of 2205Cu DSS. Under the anaerobic condition, the release of Cu ions from 2205Cu DSS had a certain bactericidal effect, reducing the metabolic activity of H. titanicae using Fe(III) as the electron acceptor. Therefore, it reduced the damage to the passivation film, inhibiting the depth of pitting corrosion of 2205Cu DSS.
This paper answered the controversial reasons for the corrosion mechanism of IRB from the perspective of the electron acceptor and its correlation with the surface characteristics of the material. It revealed the dependence of the electron acceptor of H. titanicae on the corrosion of metal materials in aerobic/ anaerobic environments. At the same time, the effects of Cu and Ni alloying elements in inhibiting the corrosion of metal materials under the action of H. titanicae were studied and compared for the first time, and the corrosion inhibition mechanisms were discussed respectively. Therefore, the work in this article had a certain theoretical guiding significance for the improvement of the marine environment MIC theory and the research of antibacterial materials.
|Subject Area||海洋科学 ; 海洋科学其他学科|
|MOST Discipline Catalogue||理学::海洋科学|
|Funding Project||Basic Scientific Research Program of Nantong[JCZ18136] ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Key Research and Development Program of China[2016YFB0300604] ; National Key Research and Development Program of China[2016YFB0300604] ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Basic Scientific Research Program of Nantong[JCZ18136]|
|Table of Contents|
|王玉. 海水环境铁还原菌Halomonas titanicae对典型金属材料腐蚀的影响机制[D]. 中国科学院海洋研究所. 中国科学院大学,2021.|
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