Microbiologically influenced corrosion (MIC) is caused by the presence and activities of microorganisms in biofilms on the surface of the corroding material. Most materials, including metals, polymers, glass and ceramics can be degraded in this manner.

Such as bacteria, fungi and algae, a number of microbiological organisms,  have been associated with corrosion damage in water systems. They can influence corrosion by effects such as differential aeration cells, the production of corrosive species such as mineral and organic acids, ammonia, and reduction of sulfate to sulfide. The various types of microbes tend to act synergistically in the corrosion of materials with their interactions typically being of a complex nature.

Even though the harmful corrosive influence of microbes has been known for more than sixty years, many practicising engineers are still surprised to learn that the activity of microorganisms can lead to severe degradation of various construction materials.

First observation

Microorganisms, including bacteria, were first observed (actually seen) in 1676 by Antoni van Leeuwenhoek, a Dutch (Delft) cloth merchant by trade but with an interest in optical microscopy.

References

• MTI Publication No.13, "Microbiologically Influenced Corrosion: A State-of-the-Art Review", Second Edition, 1989.
• P.M. Tierno: "The Secret Life of Germs", Atria, 2001.