Microbial biofilms have been identified in many studies as one of the causes for corrosion of metal surfaces through a process known as microbiologically induced corrosion (MIC). However, microbial biofilms have also been implicated more recently as inhibitors of corrosion through microbiologically influenced corrosion inhibition (MICI). What triggers MIC vs. MICI is largely unknown—in fact, some studies point to the same or similar microorganisms contributing to both induction and inhibition of corrosion, depending on environmental conditions. As such, there is a strong need for improved understanding of especially MICI processes for more effective corrosion control measures to be taken across many industries. In particular, studies must link the electrochemical processes with the microbial community and surface chemistry at the biofilm/metal interface to better characterize the MICI phenomenon. Here, we compared the corrosion outcomes of steel surfaces with environmental biofilms grown from various local soil/water sources and pure culture biofilms including Bacillus cereus, Shewanella putrefaciens, and Pseudomonas fluorescens. Upon biofilm growth and subsequent exposure to strongly corroding conditions for 14 days, some of the environmental biofilms decreased the rate of corrosion by up to 48% when compared to the abiotic control coupons. Meanwhile the B. cereus biofilm resulted in almost complete corrosion inhibition. Based on 16S rRNA gene amplicon sequencing of the environmental biofilms, the microbial communities in the biofilms were more closely related to each other, rather than the pre-biofilm environment they were sampled from. However, of the biofilm microbial communities tested only 5 species significantly (p &lt; 0.01) correlated with corrosion protection, suggesting that only a small number of bacteria may play key roles in MICI. To further explore MICI and expand to other metals, similar corrosion experiments are currently underway on aluminum surfaces with environmentally relevant microbial biofilms in which the electrochemical processes, microbial community, and biofilm chemical matrices are monitored. Our results will shed light on the complex interactions between naturally occurring microbial biofilms and metal surfaces with a focus on corrosion outcomes.

Exploring the relationship between environmental biofilms and the corrosion of metal surfaces

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