胞外聚合物对飞机油箱2024铝合金腐蚀行为影响

目的 探究飞机油箱内有积水存在的环境中硫酸盐还原菌分泌的胞外聚合物(EPS)对飞机油箱2024铝合金腐蚀行为的影响，为飞机油箱中微生物腐蚀与防护提供理论依据。方法 针对航煤中微生物滋生导致飞机油箱材料2024铝合金腐蚀失效的问题，通过傅里叶红外光谱(FT-IR)分析EPS的组成，并利用电感耦合等离子体发射光谱仪(ICP-MS)分析金属离子含量，采用表面分析法和电化学法研究了硫酸盐还原菌EPS在模拟飞机油箱积水环境中诱导飞机油箱2024铝合金的腐蚀行为。结果 与无EPS添加的介质条件相比，在相同的试验条件下，EPS导致航煤积水模拟溶液中的2024铝合金腐蚀电流密度减小，腐蚀产物膜呈疏松多孔的形貌，腐蚀形貌以点蚀为主。试验结束时，2024铝合金在EPS质量浓度为200 mg/L的模拟溶液中腐蚀速率大致为无EPS添加的模拟溶液中的1/10。当溶液中EPS质量浓度为100 mg/L和200 mg/L时，尽管EPS与Al³⁺络合产生的EPS-金属络合物会促进2024铝合金试样阳极溶解速度，但起主要影响的是抑制溶解氧扩散减缓阴极吸氧反应，抑制腐蚀的效果与EPS浓度仍成正比。结论 航煤积水模拟溶液中加入EPS会影响铝合金的腐蚀行为。当EPS质量浓度为200 mg/L时，抑制铝合金腐蚀效果最好;对于EPS质量浓度为300 mg/L的溶液，EPS-金属络合物失去隔离溶解氧作用进而加速试样腐蚀。

Influence of Extracellular Polymeric Substances on Corrosion Behavior of 2024 Aluminum Alloy in Aircraft Fuel Tank

This paper aims to explore the effect of extracellular polymeric substances (EPS) secreted by sulfate-reducing bacteria in the environment where there is water in the aircraft fuel tank on the corrosion behavior of 2024 aluminum alloy and provide a theoretical basis for microbial corrosion and protection in aircraft fuel tanks. The growth of microorganisms in aviation coal caused the corrosion failure of the aircraft fuel tank material 2024 aluminum alloy. Sulfate-reducing bacteria EPS was isolated and extracted by high-speed centrifugation. Different experimental groups were formed by adding different contents of EPS to the simulated jetting water solution. Cut the 2024 aluminum alloy into long squares of 10 mm×10 mm×3 mm as the materials and smooth them by sandpaper and cleaned. After placing the experimental groups for 11 days, Fourier transform infrared spectroscopy (FT-IR) was used to analyze the composition of EPS. The corrosion behavior of aircraft fuel tanks 2024 aluminum alloy induced by EPS of sulfate-reducing bacteria was investigated with surface analysis method and electrochemical method in a simulated aircraft fuel tank water environment. Results showed that compared with the medium condition without EPS, under the same experimental conditions, the corrosion current density of 2024 aluminum alloy decreased under the action of the EPS. The corrosion product film showed a loose and porous morphology. The corrosion morphology was dominated by pitting corrosion. Within 11 days of the experiment, the corrosion behavior was divided into three stages when the EPS concentration in the solution was 100 mg/L and 200 mg/L. In the first stage, within 3 days of the experiment, it hindered the diffusion of dissolved oxygen and inhibited corrosion to a certain extent since the EPS coated on the surface of the aluminum alloy acted as a protective layer. The second stage was in the 3-7 days of the experiment, the non-uniformity of the EPS film became larger, and the corrosive ions accelerated metal corrosion. The third stage was after 7 days of the experiment, EPS formed a stable protective film on the metal surface. It connected with various substances in the protective film to hinder the diffusion of corrosion ions and dissolved oxygen and inhibit the oxygen absorption reaction of the cathode, resulting in the corrosion rate to slow down. The EPS-metal complex produced by the complexation of EPS and Al3+ promoted the anodic dissolution rate of 2024 aluminum alloy samples, but the main influence was to inhibit the diffusion of dissolved oxygen to slow down the cathodic oxygen absorption reaction. The effect of inhibiting corrosion was still proportional to the EPS concentration. The corrosion behavior of aluminum alloy was influenced by EPS in the simulated jetting water solution. The corrosion current density of 2024 aluminum alloy in a solution with EPS concentration of 200 mg/L was roughly 1/10 times that of no EPS. When the EPS concentration was 200 mg/L, the effect of inhibiting the corrosion of aluminum alloy was the best. With 300 mg/L EPS concentration in the solution, the EPS-metal complex lost its effect in isolating dissolved oxygen and accelerated the corrosion rate of the sample.