A great new mini review (“The dual role of microbes in corrosion,” Nardy Kip and Johannes A van Vee) discussing the dual role of microbes in corrosion and corrosion inhibition has recently been published in the ISME Journal. Though not OpenAccess, because the article is so relevant to the built environment community, I wanted to highlight some of the most interesting aspects of the article here.
The first sentence of the review serves as a great reminder why all built environment researchers should be concerned about corrosion, a “global problem that affects a large variety of industries and municipal services, such as shipping, oil refinery, construction, sewage and drinking water systems, and upkeep of historical buildings and statues.” The authors then proceeding to nicely overview the ways that various microbial species are involved in corrosion of various materials (*note most corrosion is due to multispecies biofilms) and how microbes can also be used to prevent corrosion.
- two different mechanisms of iron corrosion by sulfate reducing bacteria have been described and differ based on the electron source, which is usually species-specific
- microbial assemblages can directly damage stone and concrete and also indirectly damage it because slimy biofilms retain moisture that can cause damage during freeze-thaw cycles
- microbes (bacteria and fungi) can damage stone and concrete at various sites: the stone-air interface, from within the stone (by boring into it), and at the stone-soil interface
Microbial inhibition of corrosion:
- microbially-based metal corrosion inhibition can occur in three ways (further described by Zuo 2007):
- removing corrosive substances (i.e. aerobic-respiration mediated removal of reactive oxygen)
- growth inhibition of corrosive species through production of antimicrobials by non-corrosive species
- formation of a protective layer of EPS (this is species-specific, as some EPS is protective and other EPS actually induces corrosion)
- the use of microbes to prevent stone and concrete corrosion has already been implemented for some historical buildings
- carbonatogenic bacteria precipitate carbonate, producing a substance that resembles concrete and mortar material which attaches to the structure, reinforcing it and even filling small cracks (concrete treated this way is often called “self-healing concrete”)
- calcium carbonate precipitation by some bacterial species decreases water uptake, permeability, and chloride penetration of concrete, enhancing its durability
Overall, a very interesting read that brought up some key points regarding the highly complex nature of multispecies biofilms and their role in corrosion and corrosion inhibition. Built environment researchers should keep the corrosive potential of various microbes in mind when thinking about potentially advantageous microbes in the context of the built environment.