Microbial corrosion is a term used as an abbreviation in Persian. The exact term for this corrosion is corrosion affected by microbiological factors and is introduced by the abbreviation MIC. Therefore, microbial corrosion can be defined as a type of corrosion that is intensified by the presence and activity of certain microorganisms.

Today, about one-fifth of the damage caused by corrosion in industries is related to microbial corrosion, which has received a lot of attention in recent years. Microbial corrosion is not actually corrosion, but a process that accelerates or initiates corrosion. This phenomenon can accelerate common types of corrosion. Accelerating microorganisms are able to increase the speed of common corrosion by ten times.

Microorganisms affect the corrosion rate of metal by adhering to metal surfaces and forming a thin layer of living and non-living organisms called biofilm. By forming biofilms on metal surfaces, microorganisms not only cause corrosion but also improve the conditions of the metal-environment interface in terms of corrosion. This shows the dual effect of biofilms formed on metal surfaces, which on the one hand accelerate and on the other hand moderate the corrosion rate.

The formation of biofilms on metal is the result of a microbial accumulation process. Microbial accumulation can quickly cause changes in ion concentration, environmental pH, and oxidation and reduction potential of the environment, and change the behavior of the metal against corrosion and the parameters determining its corrosion rate. These effects vary and range from intensification of the corrosion rate to prevention of corrosion. Any microbial process that facilitates one of the anodic or cathodic reactions participating in the corrosion process or causes temporary separation of the anodic and cathodic cells generally accelerates corrosion.

Microbial corrosion occurs in various industries, the most important of which are the oil and gas industries, water and wastewater industries, nuclear power plants, aircraft manufacturing industries, and metalworking industries.

To effectively control the function of microorganisms in accelerating corrosion, it is necessary to both identify the microorganisms in question and determine methods to prevent their growth.

Methods for preventing microbial corrosion

The best way to prevent microbial corrosion is to prevent the growth of biofilm. When biofilm is formed, its resistance to germicides also increases, and if this biofilm is not completely removed, it can grow rapidly. Therefore, identifying and monitoring microorganisms can be a good guide to reducing the damage caused by microbial corrosion.

• Using an adequate amount of germicide is a solution in some cases. For this purpose, microbial counting and the use of biosensors help to obtain a criterion for determining the amount of germicide required.
• Using corrosion-resistant alloys such as titanium and its alloys, which have been used in various industries for many years.
• Using various protective coatings or rutile linings on metal, sometimes protective coatings that contain germicides can also be used.
• Using the cathodic protection method.
• Using inhibitors.

Another important method for preventing microbial corrosion is biological protection mechanisms, in which biofilms are often formed, and corrosion is controlled by eliminating conditions suitable for the growth of corrosive bacteria or conditions favorable for electrochemical corrosion.