铜绿假单胞菌对2205双相不锈钢腐蚀行为的影响

Microbiologically Influenced Corrosion of 2205 Duplex Stainless Steel by Marine Pseudomonas aeruginosa

将具有(111)择优取向的岛状奥氏体相嵌入连续铁素体的2205双相不锈钢(2205 DSS)工作面浸泡在铜绿假单胞菌(P. aeruginosa)中进行电化学测试,研究浸泡时间对2205 DSS微生物腐蚀行为的影响。开路电位(OCP)、线性极化电阻(LPR)以及电化学阻抗谱(EIS)表明,在7 d浸泡期的无菌溶液中测得的EOCP、极化电阻(Rp)和电荷转移电阻(Rct)均比在有菌溶液中的大,表明铜绿假单胞菌加速了2205 DSS的腐蚀。动电位极化曲线表明,2205 DSS在无菌和有菌溶液中的维钝电流密度(ip)都随着浸泡时间的延长而不断增大,且在浸泡1 d、3 d、7 d的每个时间点有菌溶液的ip均比无菌环境的大,进一步证明铜绿假单胞菌加速了2205 DSS的腐蚀进程。扫描电子显微镜(SEM)结果表明,在有菌溶液中随着浸泡时间的延长表面粘附的细菌量逐渐增多,浸泡3 d后样品表面的细菌聚集成一个个小团簇,浸泡7 d菌落进一步聚集形成细菌生物膜。对腐蚀后样品表面局部腐蚀形貌的观察发现,细菌生物膜的形成加速了表面局部腐蚀的发生,导致严重的局部腐蚀。X射线光电子能谱(XPS)结果表明,在存在铜绿假单胞菌的条件下2205 DSS表面形成溶于水的CrO3,使MIC点蚀发生。

The MIC behavior of 2205 duplex stainless steel(2205 DSS)caused by the marine Pseudomonas aeruginosa(P.aeruginosa)with different soaking time was investigated through electrochemical testing techniques.Results show that the surface of 2205 DSS plate presents a microstructure composed of continuous ferrite matrix with uniformly distributed elongated islets of austenite phase with(111)preferred orientation.The open circuit potential EOCP,polarization resistance(Rp),and charge transfer resistance(Rct)measured in the sterile medium were larger than those in the P.aeruginosa inoculated medium during the whole soaking period of 7 d,indicating that P.aeruginosa accelerated the corrosion of 2205 DSS;The maintaining passivity current density(ip)of the 2205 DSS increases with the immersion time in both sterile and P.aeruginosa inoculated medium,whilst,the value of which during immersion in the bacterial solution was higher than that in the sterile solution for 1 d,3 d,and 7 d respectively,the fact further proved that P.aeruginosa accelerated the corrosion process of 2205 DSS;Scanning electron microscopy(SEM)results show that the amount of bacteria adhering to the steel surface gradually increased with the immersion time in the bacteria solution.After soaking for 3 days,the bacteria on the steel aggregated to form small clusters,and the bacteria aggregated to form a bacterial biofilm after 7 days.The bacterial biofilm accelerates the occurrence of pits,and later resulting in severe localized corrosion.X-ray photoelectron spectroscopy(XPS)results revealed that the water soluble CrO3 could form on the 2205 DSS surface in the P.aeruginosa inoculated medium,which may be the inducement responsible to the MIC related pitting corrosion.