采用多种电化学实验手段及场发射扫描电子显微镜(FESEM)、激光共聚焦扫描显微镜(CLSM)等分析技术,结合活死细菌染色实验、点蚀坑深度分析等方法,以316L不锈钢为对比,研究了CrCoNi中熵合金在含铜绿假单胞菌培养基中的微生物腐蚀行为。结果表明:铜绿假单胞菌能够在CrCoNi中熵合金表面形成不均匀的生物被膜,从而降低开路电位,减小极化电阻和电荷转移电阻,增大腐蚀电流密度;铜绿假单胞菌生物被膜在一定程度上破坏了钝化膜,导致浸泡在含铜绿假单胞菌培养基中的CrCoNi中熵合金的最大点蚀坑深度(4.8μm)大于无菌培养基中CrCoNi中熵合金的最大点蚀坑深度(2.3μm)。与316L不锈钢相比,CrCoNi中熵合金的开路电位较高,腐蚀电流密度和腐蚀速率较小,钝化膜的修复能力较强,在含铜绿假单胞菌培养基中浸泡后的最大点蚀坑深度小于316L不锈钢(5.8μm)。

The CrCoNi medium-entropy alloy (MEA) has excellent strength and toughness, and can be used as the basis for the development of promising engineering alloys in the future. However, microbiologically influenced corrosion (MIC) of CrCoNi MEA has rarely been reported. Especially, pseudomonas aeruginosa (P. aeruginosa) is the typical bacteria associated with MIC, which is widely distributed in the ocean and soil. It can form biofilm on the surface of steel and accelerate the corrosion of carbon steels and stainless steels (SSs). In this study, the electrochemical experiments such as open current potential (OCP), linear polarization resistance (LPR), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and cyclic polarization (CP) were used to investigate the MIC behavior of CrCoNi MEA caused by P. aeruginosa, in comparison with 316L SS. Surface analysis techniques such as FESEM and CLSM were used to observe the P. aeruginosa biofilm and pitting morphology on the coupon surface. The results show that P. aeruginosa could form an uneven biofilm on the surface of CrCoNi MEA coupons. The P. aeruginosa accelerated the corrosion rate of CrCoNi MEA, which was demonstrated by a negative shift of open circuit potential, a decrease of polarization resistance and charge transfer resistance, and an increase of corrosion current density in P. aeruginosa medium. The P. aeruginosa biofilm could destroy the passive film of the CrCoNi MEA coupons, which led to the maximum pit depth of the coupons exposed in P. aeruginosa medium (4.8 mu m) for 14 d much deeper than that in sterile medium (2.3 mu m). Compared with 316L SS, CrCoNi had higher open circuit potential, lower corrosion current density and corrosion rate, and higher repairability of passive film. Meanwhile, the maximum pit depth on the CrCoNi MEA coupons in P aeruginosa medium was shallower than that of 316L SS (5.8 mu m).