They can also act by either releasing byproducts from their cellular metabolism that corrode metals, or preventing normal corrosion inhibitors from functioning and leaving surfaces open to attack from other environmental factors.
Desulfovibrio salixigens requires at least 2.5% concentration of sodium chloride, but D. vulgaris and D. desulfuricans can grow in both fresh and salt water.
With adequate environmental factors, such as humidity, temperature, and organic carbon sources, fungi will produce colonies on concrete.
This common process among fungi allows many new fungal spores to quickly spread to new environments, developing entire colonies where nothing existed.
The mechanical pressure enables cracks to expand, leading to more moisture getting inside, and thus, the fungi have more nutrients, allowing them to travel deeper into the concrete structure.
Due to the fact that fungi expel digestive juices to gain nutrients, the structure they grow on will begin to dissolve.
It causes cracks to widen and deepen, quickly and efficiently takes root, and promotes calcium oxalate.
Aspergillus niger was the second worst offender out of the three, followed by Fusarium, which can lower the mass of concrete by 6.2 grams in a single year, as well as cause the pH to down from 12 to 8 in the same time frame.
[6] Hydrocarbon utilizing microorganisms, mostly Cladosporium resinae and Pseudomonas aeruginosa and sulfate reducing bacteria, colloquially known as "HUM bugs", are commonly present in jet fuel.
An uptick in damages on urbanized sewer systems and cities that line the coast has forced people to look further in-depth at how to preserve concrete from microbes.
Environmental stressors on structures often promote microbial corrosion caused by bacteria, Archaea, algae, and fungi.
Environmental conditions combined with carbonization caused by select microbes fabricate negative changes in the pH of the concrete.
Sewers, for example, have low oxygen levels and are high in nitrogen and sulfuric gas, making them perfect for microbes that metabolize those gases.
It can be a severely damaging phenomenon which was firstly described by Olmstead and Hamlin in 1900[8] for a brick sewer located in Los Angeles.
They can grow using oxidized sulfur compounds present in the effluent as electron acceptor and excrete hydrogen sulfide (H2S).
This gas is then emitted in the aerial part of the pipe and can impact the structure in two ways: either directly by reacting with the material and leading to a decrease in pH, or indirectly through its use as a nutrient by sulfur-oxidizing bacteria (SOB), growing in oxic conditions, which produce biogenic sulfuric acid.
Materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted for ordinary concrete or steel sewers that are not resistant in these environments.
Mild steel corrosion reduction in water by uptake of dissolved oxygen is carried out by Rhodotorula mucilaginosa(7).
The primary challenge has been finding ways to prevent or stop microbial growth without negatively impacting the surrounding environment.
Rao and Mulky[2] developed an extensive list of methods to limit the growth of microbes and therefore microbial corrosion.