4. Bacteria and corrosion of ferrous metals

The biofilm can contain various types of bacteria, depending on the distribution of the nutrients it contains. At the biofilm/solution interface, aerobic bacteria can thrive, as the oxygen concentration will be sufficient; on the other hand, at the biofilm/metal interface, where oxygen diffusion is reduced, only anaerobic and facultative aerobic bacteria will be present. Some bacteria can adapt to mixed conditions, but if the environment is unfavorable to them, they will often go into a state of "dormancy".