How does microbiologically influenced corrosion (MIC) differ from other types of corrosion?

Microbiologically Influenced Corrosion (MIC) differs from other types of corrosion in that it is caused or accelerated by the presence and activity of microorganisms, such as bacteria, archaea, and fungi, whereas other corrosion types are primarily driven by chemical or electrochemical reactions. While all corrosion involves electrochemical processes, MIC introduces biological factors that significantly alter the corrosion rate and mechanism. Microorganisms can promote corrosion in several ways, including by producing corrosive byproducts (e.g., acids, sulfides), altering the electrochemical potential of the metal surface, and forming biofilms that create localized corrosion cells. Unlike uniform corrosion, which affects the entire metal surface evenly, MIC often results in localized corrosion, such as pitting or crevice corrosion, under biofilms. The presence of MIC can be difficult to detect because the corrosion may be hidden under the biofilm and the corrosion rate can be highly variable. For example, sulfate-reducing bacteria (SRB) can cause MIC in pipelines by producing hydrogen sulfide (H2S), which is a corrosive gas that attacks the steel. Iron-oxidizing bacteria (IOB) can also cause MIC by oxidizing iron, creating tubercles of rust on the metal surface.