海洋环境腐蚀与生物污损重点实验室知识库

在海水环境中微生物会附着到海洋工程设施的表面并形成生物膜。在生物膜中多种微生物的共同作用下，海洋工程用钢的腐蚀过程会受到影响，表现出腐蚀受促进或抑制。因此，有必要对多种微生物协同作用下典型海洋工程用钢的腐蚀进行研究，揭示其腐蚀机理进而为腐蚀防护提供指导。本论文以典型海洋工程用钢为研究对象，通过实海实验、实验室模拟实验、好氧微生物与产氧微生物协同作用下的腐蚀实验，研究了其腐蚀行为；通过向基体中加入Cu元素，研究了其对微生物腐蚀（microbiologically influenced corrosion，MIC）的影响和抑制MIC的可行性；通过微生物群落分析、表面形貌观察、腐蚀产物分析和环境参数测定等方法对腐蚀机理进行了研究。主要结果如下：

（1）揭示了实海环境下Cu元素的加入对系泊链钢的腐蚀速率和表面微生物多样性的影响。发现3种试样的腐蚀速率不同：R5级钢的平均腐蚀速率最小，为0.18 ± 0.005 mm/a；较高Cu含量R6级钢的平均腐蚀速率次之，为0.24 ± 0.01 mm/a；低Cu含量R6级钢平均腐蚀速率最大，为0.34 ± 0.005 mm/a。对试样表面的微生物群落结构进行分析后发现，Cu元素的加入使得两种R6级钢样品表面硫酸盐还原菌的相对丰度均明显升高，腐蚀加速被认为与硫酸盐还原菌的富集密切相关。

（2）确定了实验室模拟实际海水条件下多种微生物对系泊链钢与碳钢腐蚀的影响规律，并解析了微生物影响的材料依赖性。在灭菌海水中，3种系泊链钢和碳钢的腐蚀行为接近，均为阴极氧去极化作用下的均匀腐蚀。在有菌海水中，微生物形成的生物膜一定程度上抑制了腐蚀的发生。但随着微生物数量的下降，腐蚀抑制作用减弱。Cu元素的加入使得两种R6级钢样品表面的微生物数量确实有所下降，但对腐蚀行为的影响不明显。碳钢由于表面发生了严重的点蚀，虽然前期腐蚀受到抑制，但最终平均腐蚀速率与无菌环境中相差不大。

（3）揭示了聚球藻与假交替单胞菌对碳钢腐蚀的协同作用机制。在单独聚球藻体系中，聚球藻生长缓慢，溶解氧浓度和pH维持相对稳定，导致了碳钢腐蚀持续地发生。在混合体系中，实验前期由于保护性生物膜的形成和假交替单胞菌好氧呼吸作用消耗溶解氧，使碳钢的腐蚀受到抑制。到实验后期，由于假交替单胞菌的死亡、聚球藻的快速繁殖、溶解氧浓度增加和疏松多孔腐蚀产物的形成，腐蚀受到促进且腐蚀失重远大于单独聚球藻体系中的。

The microorganisms would adhere to the surface of marine engineering and form biofilm in marine environment. Under the synergy of multiple microorganisms in biofilm, the corrosion of marine engineering steel would be effected, resulting in the promotion or inhibition of corrosion. Therefore, it’s necessary to study the corrosion of marine engineering steel under the synergy of multiple microorganisms, reveal the mechanism of corrosion and provide guidance to the protection of corrosion. This study investigated the corrosion behavior of typical marine engineering steel through the exposuretest in marine, the simulated experiment in laboratory, and the corrosion experiment under the synergy of aerogenic and aerobic bacteria. It investigated the effects of adding Cu to the matrix on the microbiologically influenced corrosion (MIC) and the feasibility to inhibit it. It revealed the corrosion mechanism through the analysis of microbiology community, the observation of surface morphology, the analysis of corrosion products, and the measurement of environmental parameters. The results are as followed:

(1) The effects of the addition of Cu on the corrosion rate and surface microbial diversity of mooring chain steel were revealed in marine environment. The corrosion rates of 3 kinds of samples were different with each other: the average corrosion rate of R5 steel was 0.18 ± 0.005 mm/a, which was the least; the average corrosion rate of R6 steel with a higher and lower content of Cu was 0.24 ± 0.01 and 0.34 ± 0.005 mm/a, respectively. The analysis of microbiology community structure on the surface of samples suggested that the addition of Cu increased the relative abundance of sulfate‒reducing bacteria (SRB) on the surface of both R6 samples, which was believed to closely relate to the accelerated corrosion.

(2) The effects of multiple microorganisms on the corrosion of mooring chain steel and carbon steel were revealed, and the material dependence of the effects of microorganisms was analysed under the condition of simulated seawater in laboratory. The results suggested that the corrosion behavior of carbon steel and 3 kinds of mooring chain steel was similar in sterile seawater, which were general corrosion induced by the cathodic oxygen depolarization. In seawater with bacteria, the biofilm formed by microorganisms inhibited the corrosion to a certain extent. The microorganism quantity decreased with time, leading to the weakened inhibition. The addition of Cu resulted in the decrease of microorganism quantity on the surface of both R6 samples, but it made little impact on the corrosion behavior. Though corrosion was inhibited in the intial stage, the average corrosion rate of carbon steel was similar with the case in sterile seawater, which could be attributed to the serious pitting corrosion.

(3) The mechanism of the corrosion of carbon steel was revealed under the synergy of Synechococcus sp. (S. sp.) and Pseudoalteromonas sp. (P. sp.). In the media containing S. sp. alone, it propagated slowly, and dissolved oxygen concentration and pH maintained relatively stable, resulting in a continuous corrosion of carbon steel. In the presence of S. sp. and P. sp., corrosion was inhibited in the intial stage by the formation of protective biofilm and the consumption of oxygen by aerobic respiration of P. sp. In the later part of experiment, a serious corrosion on carbon steel was observed due to the death of P. sp., the rapid reproduction of S. sp., the increase of dissolved oxygen concentration, and the porous corrosion products, in which the corrosion rate was much higher than it in the media with S. sp. alone.