海洋耗氢微生物对高强度钢阴极保护的作用规律与机理

This research aims to solve the fundamental theory of reducing the risk of hydrogen embrittlement when cathodic protection is applied on high strength steel utilizing hydrogen consuming microorganisms. The superior performance of high strength steel can meet the requirements on material strength for far, deep sea marine engineering development. But due to the severe corrosive marine environment, the steel must be protected. Cathodic protection is the commonly used and effective method in preventing the corrosion of iron and steel materials in full seawater immersion and sea mud zones. Appropriate applied cathodic potential can prevent iron and steel component from corrosion. However, the high strength steel is sensitive to hydrogen embrittlement, and cathodic protection can promote hydrogen permeation into steel, increasing the brittleness as a result of hydrogen content increase. With the strength increasing, the risk of hydrogen embrittlement increases gradually, restricting the development of far, deep sea marine engineering. At present, although the hydrogen embrittlement resistance of high strength steel is improved from the aspects of microstructures’ optimization, hydrogen embrittlement is still not radically solved for high strength steel in marine resources development and applications. In practical engineering applications, the risk of hydrogen embrittlement is usually increased due to over negative cathodic protection potential, with material properties decreasing or losing as a consequence. In marine environment, over negative cathodic potential may lead to brittle fracture, not only causing serious economic losses, but also the occurrence of disastrous accidents. The material that is not too sensitive to hydrogen embrittlement is due to lower hydrogen diffusion rate and the cathodic protection potential can be lowered. But the common law is that in order to prevent the deteriorating of material properties under cathodic protection conditions, the selected potential is higher than the ideal potential. In fact, the ideal protection is not reached and corrosion still occurs on material surface. There is a kind of widespread hydrogen consuming microorganisms in natural environment, utilizing the energy of hydrogen oxidation to maintain life. If we can utilize the hydrogen consuming function of this kind of microorganisms to consume the hydrogen generated in the process of cathode protection, reducing the amount of hydrogen’s penetrating into material, then the potential can be reasonably lowered, making the steel ideally protected to a minimum corrosion rate and reducing the possibility of hydrogen embrittlement’s occurring at the same time. This will play an important role for the safety application of high strength steel in marine environment. If this aim can be achieved, it will be very important for the safety application of high strength steel in marine environment, having broad application prospects. Therefore, it is necessary to carry out the research on the regularity and mechanisms of the effects of marine hydrogen consuming microorganisms on cathodic protection of high strength steel, investigating the effects of the microorganisms on cathodic polarization behavior, finding out the hydrogen permeation behavior under cathodic protection in environment containing hydrogen consuming microorganisms, studying the feasibility of using hydrogen consuming microorganisms in decreasing the danger of hydrogen embrittlement of high strength steel under cathodic protection potential, characterizing the morphology and structure of the film of hydrogen consuming microorganisms on the surface of material, so as to provide a theoretical support for improving the safety and reliability of high strength steels in marine applications through utilizing the hydrogen consuming function of microorganisms and the development of bionic technology.

本项目拟解决利用耗氢微生物降低阴极保护下高强度钢发生氢脆风险的基础理论问题。深远海开发使高强度钢在海洋工程中的应用不断增加。但由于海洋环境的强腐蚀性，必须对其进行保护。阴极保护是常用且有效的腐蚀防护方法。可是，高强度钢对氢脆敏感，阴极保护可促进氢向钢中渗透，增加发生氢脆的危险。如能利用自然环境中广泛存在的耗氢微生物消耗阴极保护过程中产生的氢，抑制氢的渗透，就可适当降低阴极保护电位，使高强度钢的腐蚀既得到有效控制又不增加发生氢脆的危险性。这一目标的实现对高强度钢在海洋环境中的安全应用有十分重要的意义，有广阔的应用前景。因此，有必要开展海洋耗氢微生物对阴极保护的作用规律与机理的研究，考查耗氢微生物对低合金高强度钢阴极极化行为的影响，对材料表面耗氢微生物膜的形态、结构进行表征，弄清耗氢微生物作用下低合金高强度钢的氢渗透行为特征，为利用耗氢微生物和发展仿生技术提高高强度钢的安全可靠性提供理论支撑。

低合金高强度钢具有节约资源、降低建设成本等优点，但对氢脆敏感。在海洋环境中，不恰当的阴极保护电位会促进氢向钢中渗透，增加发生氢脆的危险。如果能利用自然界中广泛存在的耗氢微生物消耗阴极保护过程中产生的氢，抑制氢的渗透，就可以适当降低阴极保护电位，实现对高强度钢的完全保护。本项目研究了耗氢微生物（Blautia coccoides GA-1）对AISI 4135钢腐蚀行为的影响。结果表明，AISI 4135钢在自腐蚀电位下的腐蚀速率与菌株GA-1的菌量成正相关。菌株GA-1可以从AISI 4135钢表面直接或间接获得电子，但该过程不是导致钢腐蚀的主要原因。在此基础上研究了菌株GA-1对AISI 4135钢氢渗透行为的影响，通过氢渗透效率对微生物的耗氢作用进行表征。结果表明，附着于金属表面的菌株GA-1细胞可以直接从阴极表面附近获得新产生的氢原子[H]，并降低表面吸附氢浓度，从而减少了氢的吸收比例并导致氢渗透效率降低。过负的阴极保护电位抑制了菌株GA-1细胞的附着，使其耗氢作用较弱。在较小的恒电流极化条件下，菌株GA-1可以有效地消耗阴极氢，从而降低氢渗透电流。慢应变速率拉伸试验结果表明，阴极极化和菌株GA-1的存在均可增加AISI 4135钢氢脆敏感性。尽管菌株GA-1具有消耗阴极氢的作用，降低了氢渗透效率，但同样由于其副作用的存在，导致了AISI 4135钢表观氢脆敏感性的增强。因此，在增强耗氢微生物消耗阴极氢的作用的同时，减弱微生物存在所带来的副作用是将来利用耗氢微生物抑制氢脆的关键。本项目系统研究了耗氢微生物对高强度钢阴极保护过程、氢渗透行为以及力学行为的的影响、作用规律与机理，分析了利用耗氢微生物抑制高强度钢氢脆的可行性，这一目标的实现对高强度钢在海洋环境中的安全应用有十分重要的意义，前景广阔。