Microbial corrosion refers, by definition, to the degradation of materials due to the activity of a wide variety of microorganisms, usually embedded in a gel matrix—the biofilm—attached to the surface. The feature of MIC (microbial induced corrosion) is connected to three factors: microorganisms involved (bacteria, algae, moulds or fungi, individually or in combination), material, and environment (solution and conditions). 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, for example, sulfuric and carbonic acids, hydrogen sulfide 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., sulfur). Remedial actions are similar to those taken to avoid corrosion, but must be applied much more rigorously, as once it starts, it is extremely difficult to stop MIC. Preventive actions include optimum design of the plant at the early stage and proper material selection based on expected operative and environmental conditions.