海洋环境腐蚀与生物污损重点实验室知识库

军舰民船等在实海中执行防护任务开展运输作业，海水环境中种类繁多的微生物附着在其表面代谢增殖形成生物膜。多种微生物协同作用影响船体结构材料的腐蚀过程，导致材料腐蚀的加剧或抑制。研究多种微生物协同作用下船体结构材料的腐蚀过程，对于揭示腐蚀机理、提供腐蚀防护指导都有十分重要的理论和实际意义。本论文以船体结构材料907钢为研究对象，先后进行了实海挂片实验、实验室模拟实海实验、单种微生物以及好氧与厌氧微生物协同作用下的腐蚀实验。采用涂布分离培养法和宏基因组高通量测序技术分离、提纯、培养并鉴定腐蚀微生物，研究其微生物群落丰富度、多样性和组成结构信息。采用丝束电极技术和电化学阻抗方法研究腐蚀电化学行为，采用扫描电子显微镜、X-射线光电子能谱、X-射线衍射观察腐蚀形貌、分析腐蚀产物组成，采用激光共聚焦显微镜和荧光显微镜观察生物膜形成和分布，监测体系DO和pH等环境参数的变化。综合以上结果归纳腐蚀特点、解析腐蚀机制，主要的研究内容如下：

（1）探讨了海域、腐蚀区带、暴露时间等因素对907钢的腐蚀影响。结果表明，同一海域相同腐蚀区带浸泡6个月试样腐蚀速率高于浸泡3个月试样；同一海域相同浸泡时间潮差区腐蚀速率大于全浸区；相同腐蚀区带相同浸泡时间三亚海域腐蚀速率大于青岛海域。907钢实海挂片腐蚀产物组成变化不大主要为Fe₃O₄、a-FeOOH、g-FeOOH等，另外CaCO₃混杂附着在腐蚀产物中并可不断积累。多种微生物实海共存，三亚海域分离得到可培养微生物种类高于青岛海域，SRB普遍存在于不同海域全浸区各实验时长907钢腐蚀产物中，受时空条件影响，微生物分离结果不同且分布随条件改变发生变化。

（2）探讨了实海环境下907钢腐蚀产物层中微生物群落结构的多样性。结果发现，在青岛海域全浸区挂片3个月907钢的腐蚀速率约为0.23 mm/a，腐蚀产物主要为α-FeOOH、γ-FeOOH、γ-Fe₂O₃和Fe₃O₄，腐蚀形式为均匀腐蚀。腐蚀产物内层微生物群落的丰富度和多样性均高于外层样品。内外层腐蚀产物OTU数分别为1763和1691，共有OTU数为941。内外层SRB的OTU数目分别为908和798，其中共有OTU数目为438。内外层样品在属水平的共有群落主要为贪铜菌、鞘氨醇单胞菌、乳杆菌和苍白杆菌。内外层共有SRB在属水平菌群主要为脱硫弧菌、脱硫杆菌、色菌。

（3）构建实海模拟体系，研究了微生物对907钢腐蚀行为的影响。微生物使得907钢的腐蚀速率略有降低，由约0.0727 mm·a^-1降低到约0.0615 mm·a^-1。微生物改变了腐蚀形貌与腐蚀产物组成，无菌体系针片状腐蚀产物尺寸逐渐增大并堆叠成簇覆盖样品表面，腐蚀产物为Fe₃O₄、FeCO₃和FeOOH；有菌体系微生物与代谢产物不均匀分散于样品表面形成生物膜，腐蚀产物为FeS和Fe₃O₄。微生物代谢类型、生物膜形成发展以及代谢产物性质综合影响腐蚀过程。微生物的好氧代谢抑制氧在阴极的去极化反应、降低反应速率。生物膜在实验初期形成阻碍电荷传递转移、实验后期破损导致腐蚀抑制作用弱化。微生物生命活动积累的有机酸使溶液pH降低，对腐蚀有促进作用。实验后期SRB的生长代谢亦能促进腐蚀。各因素综合影响，腐蚀抑制作用强于腐蚀促进作用。

（4）揭示了脱硫弧菌对907钢腐蚀过程的影响与作用机制。研究发现，在无氧海水培养基条件下907钢的腐蚀速率与脱硫弧菌生长曲线变化趋势一致。脱硫弧菌代谢形成不均匀生物膜，去除腐蚀产物后局部出现孔蚀，FeS为主要的腐蚀产物。脱硫弧菌对907钢腐蚀机制的影响可能源于代谢产物H₂S阴极去极化作用对局部微观电化学性质的改变。无菌介质中，i_max数值持续减小腐蚀没有深入发展。活性阳极位点位置不固定导致大面积阳极区形成并发生均匀腐蚀。脱硫弧菌介质中，电化学活性位点生成后保持稳定最终形成大阴极小阳极的特征电流分布促进阴极去极化作用促进局部孔蚀的形成和发展。

（5）构建脱硫弧菌和溶藻弧菌共同作用下的实验体系，研究两种微生物对907钢的腐蚀行为及腐蚀机理的共同影响。研究发现，海水条件脱硫弧菌和溶藻弧菌共同作用改变907钢的腐蚀速率、腐蚀类型、产物成分和腐蚀程度。无菌体系腐蚀速率约为0.2 mg·cm^-2·d^-1，发生均匀腐蚀且程度较深，腐蚀产物主要为FeOOH、Fe₃O₄和FeCO₃。混合菌体系腐蚀速率约为0.07 mg·cm^-2·d^-1，发生程度较轻的局部腐蚀且腐蚀产物中出现FeS。溶藻弧菌消耗海水中溶解氧代谢生成生物膜抑制腐蚀的深入发生并且创造脱硫弧菌生存所需的无氧微环境。脱硫弧菌的生命活动改变了生物膜的结构和形态，但其对腐蚀的促进作用未占主导地位。

Warships and civilian ships carry out protection tasks and transport operations in the real sea. A variety of microorganisms in the seawater environment adhere to their surface to metabolize and proliferate to form biofilms. The synergistic action of various microorganisms affects the corrosion process of hull structural materials, which leads to corrosion aggravation or inhibition. It is of great theoretical and practical significance to study the corrosion process of hull structural materials under the synergistic action of various microorganisms. In this thesis, the hull structure material 907 steel was taken as the research object, and the corrosion experiments were carried out successively, including sea hanging test, laboratory simulated real sea test, single microorganism and the synergistic action of aerobic and anaerobic microorganisms. Corrosive microorganisms were isolated, purified, cultured and identified by coating culture method and high-throughput sequencing technology, and their community richness, diversity and structure information were studied. The electrochemical behavior of corrosion was studied by wire beam electrodes and electrochemical impedance spectroscopy. The corrosion morphology was observed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and the composition of corrosion products were analyzed. The formation and distribution of biofilm were observed by confocal laser microscopy and fluorescence microscopy, and the changes of environmental parameters such as DO and pH were monitored. Based on the above results, the corrosion characteristics and mechanism are summarized and analyzed. The main research contents are as follows:

(1) The effects of sea area, corrosion zone and exposure time on the corrosion of 907 steel were discussed. The results showed that the corrosion rate of samples immersed in the same corrosive zone for 6 months was higher than that of samples immersed in 3 months in the same sea area. The corrosion rate of the tidal zone in the same immersion time was higher than that of the whole immersion area. The corrosion rate of Sanya sea area in the same corrosive zone was higher than that of Qingdao sea area in the same immersion time. The composition of corrosion products of 907 steel seamount had little change, mainly consisting of Fe₃O₄, a-FeOOH, g-FeOOH and so on. In addition, CaCO₃ mixed with corrosion products could accumulate continuously. Many kinds of microorganisms coexisted in the real sea. The number of culturable microorganisms isolated from Sanya sea area was higher than those from Qingdao sea area. SRB was ubiquitous in the corrosion products of 907 steel in the full immersion zone of different sea areas. Under the influence of space-time conditions, the results of microbial isolation were different and the distribution changed with the change of conditions.

(2) The effects of real sea environment on corrosion behavior and microbial community diversity of 907 steel were discussed. The results showed that the corrosion rate of 907 steel hanging in the full immersion zone of Qingdao sea area for three months was about 0.23 mm/a. The corrosion products mainly consisted of a-FeOOH, g-FeOOH, g-Fe₂O₃ and Fe₃O₄. The corrosion forms were uniform corrosion. The richness and diversity of microbial communities in the inner layer of corrosion products were higher than those in the outer layer. The number of OTUs of inner and outer corrosion products was 1763 and 1691, respectively, and the common number of OTUs was 941. The number of OTUs of inner and outer SRB was 908 and 798, respectively, and the common number of OTUs was 438. Common communities of inner and outer samples at generic level were mainly Cupriavidus, Sphingomonas, Lactobacillus and Ochrobactrum. There were SRB bacteria in the inner and outer layers at genus level, Desulfovibrio, Desulfobacter and Allochromatium were the main gena.

(3) The effect of microorganisms on corrosion behavior of 907 steel was studied by building a real sea simulation system. The corrosion rate of 907 steel was slightly reduced by microorganisms, from about 0.0727 mm/a to about 0.0615 mm/a. Microorganisms changed the corrosion morphology and composition of corrosion products. The size of needle-like corrosion products in the aseptic system increased gradually and covered the surface of samples in clusters. The corrosion products were Fe₃O₄, FeCO₃ and FeOOH. The microorganisms and metabolites in bacterial system were dispersed unevenly on the surface of samples to form biofilms, and the corrosion products were FeS and Fe₃O₄. The types of microbial metabolism, the formation and development of biofilm and the properties of metabolites affected the corrosion process comprehensively. Aerobic metabolism of microorganisms inhibited the depolarization reaction of oxygen in the cathode and reduced the reaction rate. The formation of biofilm in the early stage of the experiment hindered charge transfer, and the later stage of the experiment led to the weakening of corrosion inhibition. Organic acids accumulated by microbial life activities could reduce the pH of solution and promote corrosion. The growth and metabolism of SRB could also promote corrosion in the later stage of the experiment. The inhibition of corrosion was stronger than the promotion of corrosion.

(4) The effect and mechanism of Desulfovibrio sp. on corrosion process of 907 steel were revealed. It was found that the corrosion rate of 907 steel in anaerobic seawater medium was consistent with the growth curve of Desulfovibrio sp.. Desulfovibrio sp. metabolized to form an inhomogeneous biofilm. After removing the corrosion products, local pitting occurred. FeS was the main corrosion product. The effect of Desulfovibrio sp. on corrosion mechanism of 907 steel might be due to the change of local micro-electrochemical properties caused by the cathodic depolarization of the metabolite H₂S. In aseptic media, the continuous decrease of i_max value had not been further developed. The location of active anode sites was not fixed, resulting in the formation of a large area of the anode and uniform corrosion. In Desulfovibrio sp. medium, the characteristic current distribution of large cathode and the small anode was stable after the formation of electrochemically active sites, which promoted the formation and development of local pitting.

(5) An experimental system under the combined action of Desulfovibrio sp. and Vibrio alginolyticus was constructed, and the joint effect of the two microorganisms on the corrosion behavior and corrosion mechanism of 907 steel were investigated. It was found that the corrosion rate, corrosion type, product composition and corrosion degree of 907 steel were changed by the interaction of Desulfovibrio sp. and Vibrio alginolyticus under seawater conditions. The corrosion rate of aseptic system was about 0.2 mg·cm^-2·d^-1, and the corrosion products were mainly FeOOH, Fe₃O₄ and FeCO₃. The corrosion rate of mixed bacteria system was about 0.07 mg·cm^-2·d^-1. The local corrosion was mild, and FeS appeared in the corrosion products. Vibrio alginolyticus consumed dissolved oxygen in seawater to produce biofilm to inhibit corrosion and created anaerobic microenvironment for Desulfovibrio sp. to survive. Desulfovibrio sp. had changed the structure and morphology of biofilm, but its promotion to corrosion was not dominant.