Microbial, Corrosion

Microbial corrosion refers, by definition, to the deterioration of materials caused, directly or indirectly, by bacteria, algae, moulds or fungi, individually or in combination. In particular, degradation of metallic structures derives from the activity of a wide variety of microorganisms either directly participating in electrochemical reactions on the metal surface or producing aggressive metabolites capable of making the environment corrosive. A wide range of microorganisms may be involved in corrosion processes such as: chemical attack of metals, concrete and other materials, by means of the by-products of microbe metabolism e.g. sulphuric and carbonic acids, hydrogen sulphide or ammonia; attack of metal by a process in which the corrosion reaction is sustained by the combined action of microbes and metal or by a combination of bacteria; depassivation of metal surfaces and induction of corrosion cells; depolarization of cathodic reaction; microbial attack of organic materials (e.g. paint coatings, plastic linings), degradation of inhibitors, conversion of natural inorganic compound (e.g. sulphur).