目的 从切削废液中分离出类产碱假单胞菌(Pseudomonas pseudoalcaligenes)菌株，研究该菌株对切削液的劣化，以及5754铝合金在含该菌株的切削液中的微生物腐蚀(MIC)行为。方法 采用平板划线法，从切削废液中分离提纯出单一菌株，并通过16S rDNA进行菌株测序。将类产碱假单胞菌接种至切削液中，并将5754铝合金金浸泡于其中。通过定期检测细菌在切削液中的生长状况、切削液的pH值、乳液液滴粒径、溶解氧、总有机碳(TOC)、无机碳(IC)以及总氮(TN)含量变化，分析微生物对切削液的劣化行为。通过表征铝合金在含菌切削液中的微观腐蚀形貌与生物附着情况，并结合电化学手段，分析5754铝合金在含菌切削液中的电化学腐蚀行为。结果 类产碱假单胞菌在切削液中具有良好的生长状况，微生物浓度维持在10⁷ CFU/mL以上。切削液发生了严重的生物降解，在实验周期内，pH值由9.25降至7.39，乳液液滴粒径分布曲线从单峰分布(1.07 μm)变为双峰分布(1.12、8.93 μm)，染色后的液滴有明显增大，并观测到了液滴间的聚结。切削液中TOC的质量浓度由15.42 g/L下降至9.69 g/L，IC由189.03 mg/L上升至485.50 mg/L，TN由564.77 mg/L下降为142.16 mg/L。5754铝合金在含菌切削液中浸泡10 d时，表面出现了生物膜;浸泡15 d后，金属基体在生物膜下发生了严重的点蚀现象。极化曲线结果显示，腐蚀电位(Ecorr)发生了明显的负移，铝合金的腐蚀电流密度(Jcorr)由0.274 μA/cm²上升至0.477 μA/cm²。在15 d时，铝合金的腐蚀电流密度要比在无菌切削液中高出4.9倍。铝合金的击穿电位也不断负移，使得铝合金极易发生点蚀。EIS结果显示，随着浸泡时间的增加，5754铝合金的阻抗弧半径不断变小，铝合金的耐腐蚀性不断变差。结论 类产碱假单胞菌将切削液中缓冲剂、乳化剂等含氮有机物优先降解为可溶性无机盐，使切削液pH降低，乳化剂保护效果下降，溶液导电性增加，使劣化后的切削液更具腐蚀性。类产碱假单胞菌在5754铝合金表面形成生物膜，不断消耗金属表面的氧气，使铝合金无法维持钝化膜的完整性，金属基体在生物膜下不断发生腐蚀，耐腐蚀性能下降，并形成严重的点蚀。

We investigated the corrosion behavior of 5754 aluminium alloy in metalcutting fluid (MCF) containing P. pseudoalcaligenes which was isolated from a waste metalcutting fluid (WMCF). The single strain was purified and isolated by streak plate method and sequenced using 16S rDNA. P. pseudoalcaligenes was inoculated into the MCF and 5754 aluminium alloy specimen were immersed in the bio-contaminated MCF simultaneously. pH, emulsion droplets size distribution, dissolved oxygen, TOC, IC, and TN in the MCF were investigated to analysis the biodeterioration of MCF under the influence of P. pseudoalcaligenes. The microbially influenced corrosion behavior of 5754 aluminium alloy in the MCF was characterized by morphological characterization of metal and the attachment of biofilm. The polarization curves and EIS were applied to analyze the electrochemical behavior of aluminium alloy in the MCF containing P. pseudoalcaligenes. Remarkable growth of P. pseudoalcaligenes was showed in the MCF and the biomass remained at 107 CFU/mL. A severe biodegradation of MCF was observed, with the pH decreased from 9.25 to 7.39 and the curve of emulsion droplets size distribution transforming into bimodal (1.12 μm, 8.93 μm) from monomodal (1.07 μm). The coalescence between emulsion droplets was observed after the staining of droplets. The change of TOC and TN showed a decline from 15.42 g/L and 564.77 mg/L into 9.69 g/L and 142.16 mg/L, respectively. And the increase of IC was obtained during the biodegradation. A biofilm was occurred on the surface of 5754 aluminium alloy immersed in MCF containing P. pseudoalcaligenes for 10 days and a seriously pitting was observed in the matrix under the biofilm after immersion for 15 days. Results of polarization curve showed that the Ecorr shifted negatively under the microbial influence. The Jcorr of aluminium alloy immersed in MCF with microbes for 15 days increased from 0.274 μA/cm2 to 0.477 μA/cm2. The Jcorr of aluminium alloy immersed in bio-contaminated MCF for 15 days was 4.9-fold greater than in the absence of bacteria. The pitting was easily occurred on the surface of metal due to the negative shift of pitting potential. Result of EIS presented that the semidiameter of impedance was decreased with the extension of immersion time. The resistance of corrosion of 5754 aluminium alloy was weakened under the presence of P. pseudoalcaligenes. P. pseudoalcaligenes preferentially degraded the nitrogen-containing organic compounds such as buffer and emulsifier into soluble inorganic salts, which reduced the pH value of cutting fluid and the protective effect of emulsifier and increases the conductivity of solution, making the deteriorated cutting fluid more corrosive. The aluminium alloy showed more corrosive in an aggressive media. Oxygen was almost consumed by bacteria in the biofilm. The passivating film of Al2O3 was incomplete to protect matrix due to the lack of oxygen which led to the pitting under the biofilm.