热带海洋气候下海水中45钢的硫氧化菌腐蚀研究

Our previous research results showed the drastically increased corrosion rates of carbon steel in sea water in tropical maritime climate were concomitant with the high quantity of sulfur-oxidizing bacteria (SOB) in the corrosion product of carbon steel. At the same time, serious pitting corrosion was found on the surfaces of carbon steel. In addition, our preliminary work indicated SOB not only increased the corrosion rates of 45 steel but also be responsible for serious pitting corrosion and lots of grooving corrosion in sea water inoculated with SOB. So far the systemic research is scarce on the corrosion of metal materials by SOB. In this research project, we will investigate the distribution of SOB communities in the corrosion product of 45 steel in sea water in tropical maritime climate by 16S rRNA gene high-throughput sequencing. The different species of SOB will be separated and identified from the corrosion product of 45 steel. Then a systemic comparative study will be carried out between the corrosion behaviors of 45 steel in sea water inoculated with the different species of SOB respectively and those in sterile sea water in tropical maritime climate by mass loss experiments, electrochemical methods and surface characterization techniques, in order to understand the effects of the different species of SOB on the uniform corrosion and localized corrosion behaviors of 45 steel in sea water and the mechanisms of the effects. Together with the distribution of SOB communities in the corrosion product of 45 steel, the results will illustrate the key SOB communities responsible for the corrosion of 45 steel. This research project will contribute to the clarification of the MIC of carbon steel in sea water in tropical maritime climate and its mechanisms.

本研究小组前期研究工作表明，热带海洋气候下海水中碳钢腐蚀速率的大幅度提高伴随着腐蚀产物中硫氧化菌的大量出现，同时碳钢表面出现严重的点蚀；此外，我们对45钢在硫氧化菌海水溶液中腐蚀的初步研究显示，硫氧化菌不但提高了腐蚀速率，而且造成了严重的点蚀和大量罕见的腐蚀沟。然而关于金属材料硫氧化菌腐蚀的系统研究相当缺乏。本项目拟运用16S rRNA基因高通量测序，深入分析热带海洋气候下45钢海水腐蚀产物中硫氧化菌的群落分布；将45钢腐蚀产物中的硫氧化菌分离鉴定到种水平；运用失重法、电化学技术和表面表征技术，系统深入地对比研究热带海洋气候下45钢在分别含有各种硫氧化菌的海水、灭菌海水中的腐蚀行为，探索海水中不同种硫氧化菌对45钢的均匀腐蚀和局部腐蚀行为的影响及作用机理，结合硫氧化菌的群落分布研究结果，分析腐蚀碳钢的主要硫氧化菌，从而进一步揭示热带海洋气候下海水中碳钢的微生物腐蚀作用及作用机制。

碳钢由于具有经济、优异的力学性能的特点，使其在海洋设施与船舶建造等领域被广泛使用，因此碳钢在海洋环境下的腐蚀与防护值得被关注。另一方面，热带海洋气候下海水中微生物的存在显著影响碳钢的腐蚀速率。本研究小组在前期的研究基础上，对硫氧化菌（SOB）影响碳钢腐蚀的行为和机理进一步探究。具体研究过程为，选取了在海水浸泡7、14和30d的45钢的腐蚀产物，对腐蚀产物中的所有微生物进行基因组DNA的提取，通过PCR扩增及高通量测序的方法测定所有的16S rRNA基因序列，得到腐蚀产物中的硫氧化菌（SOB）的丰度随着腐蚀时间延长而增加，并且腐蚀产物中细菌群落的多样性为：14d> 7d> 30d。进一步对腐蚀产物中的硫氧化菌（SOB）进行分离和纯化，并将其鉴定到种水平，鉴定出的5种硫氧化菌（SOB）分别为Halomonas denitrificans、Chromohalobacter israelensis、Thioclava dalianensis、Alcanivorax sp.和Bacillus aquimaris。海水中和腐蚀产物中的Rhodotorula mucilaginosa和Halomonas denitrificans的细胞数量包含生长期、稳定期和衰亡期三个阶段。最后研究了各种硫氧化菌（SOB）对45钢的腐蚀行为，其中Halomonas denitrificans的存在降低了45钢的短期均匀腐蚀速率，但增加了长期均匀腐蚀速率，并增强了45钢的局部腐蚀；Rhodotorula mucilaginosa减缓了45钢的均匀腐蚀速率，也降低了局部腐蚀。Chromohalobacter israelensis、Thioclava dalianensis、Alcanivorax sp.和Bacillus aquimaris在短期内均抑制了45钢的均匀腐蚀速率，而Thioclava dalianensis增加了45钢的长期均匀腐蚀速率。XPS分析表明，在无菌海水中和有SOB的海水中碳钢腐蚀产物均为Fe2O3和Fe3O4。本项目的研究为海洋工程设计提供直接依据，并为碳钢在海洋设施中的安全使用及其防护工作提供理论依据。