Bacterial anaerobic corrosion
Bacterial anaerobic corrosion is a bacterially-induced oxidation of metals.
In a humid environment and anoxic conditions the corrosion of metals occurs as a result of a redox reaction that generates molecular hydrogen from hydrogen ions, requiring bacteria, unlike anaerobic corrosion that occurs spontaneously.
A base metal, such as iron goes into aqueous solution as positively charged cation, Fe2+. As the metal is oxidized under anaerobic condition by the protons of water, H+ ions are reduced to form molecular H2. This can be written in the following ways under acidic and neutral conditions respectively:
Usually, a thin film of molecular hydrogen forms on the metal. Sulfate-reducing bacteria, oxidize the molecular hydrogen to produce hydrogen sulfide ions and water:
The iron ions partly precipitate to form iron sulfide. A reaction with water also occurs, producing iron hydroxide.
The net equation comes to:
This form of corrosion by sulfate-reducing bacteria can, in this way, be far more harmful than anaerobic corrosion.
