X80管线钢表面SRB生物膜特征及腐蚀行为

Characteristics of SRB Biofilm and Microbial Corrosion of X80 Pipeline Steel

采用SEM、Raman光谱、XPS等分析手段,结合扫描振动电极(SVET)、微区电化学测试和电化学阻抗谱(EIS)等电化学测量技术,研究含硫酸盐还原菌(SRB)的模拟海水中X80管线钢表面生物膜的形成、特征,生物膜与膜下金属的交互作用,以及管线钢腐蚀行为及电化学过程特征。结果表明:SRB微菌落及胞外聚合物(EPS)形成初期,EPS的屏障作用抑制X80钢的腐蚀过程;SRB生物膜形成后,X80钢的自然腐蚀电位降低约20 mV,SRB显著促进了管线钢的腐蚀过程;浸泡后期SRB及其生物膜使X80钢腐蚀速率较灭菌对照组高出约1个数量级。SRB生物膜与腐蚀产物Fe2+/Fe3+间存在络合、螯合作用,细胞及其代谢产物硫化物与金属间存在直接或间接电子交互作用,这些作用相互协同耦合,促使生物膜下局部腐蚀的发生和发展。

Microbiologically induced corrosion （MIC） is known as one of the most damaging failures for pipeline steels. Especially, sulfate-reducing bacteria （SRB） is the most widespread strains in soil and seawater environments and is the typical bacteria associated with MIC. SRB may cause severe localized attack, leading to pipeline failures in forms of pitting, crevice corrosion, dealloying and cracking. In this work, SEM, Raman spectroscopy, XPS, scanning vibrating electrode （SVET） technique, EIS and other electrochemical techniques were used to study the formation of SRB biofilm, its electrochemical interaction with X80 pipeline steel and corrosion behavior of the steel in a simulated seawater. The results showed that barrier effect of the extracellular polymer substances （EPS） inhibits corrosion process of X80 steel in the initial formation of EPS and SRB micro-colony. After the formation of SRB biofilm, open circuit potential （EOCP） of the steel decreases 20 mV, and SRB significantly promotes the corrosion process of the pipeline steel. In the later stage, due to SRB and its biofilm, the corrosion rate of X80 steel exposed in SRB inoculated environment is almost one order of magnitude higher than that in the sterile environment. The biofilm have complexation effect and chelation effect with corrosion products （Fe2＋/Fe3＋）. SRB cells, metabolites and biofilms have direct and indirect electron interactions with the steel substrate. These various coupling effects promote occurrence and development of local corrosion on the surface of the steel beneath biofilm.