Which corrosion occurs under a bacteria colony in low-flow areas and is prevented by periodic cleaning and biocides?

• A. Ion Exchangers
• B. Crevice corrosion
• C. Pitting corrosion
• D. Microbiologic corrosion

Answer: (D)

Microbiologic corrosion, also known as MIC, happens when bacteria form a biofilm on metal surfaces in areas with little or no flow. The biofilm creates a microenvironment where bacteria can thrive and produce corrosive byproducts, such as sulfides and organic acids, and it can also drive differential aeration that accelerates localized attack beneath the film. In low-flow zones, stagnant water promotes biofilm growth, making the underlying metal more susceptible to corrosion.

Periodic cleaning removes the biofilm physically, and biocides kill the bacteria, breaking up the biofilm and stopping the microbial contribution to corrosion. The other forms of corrosion—crevice, pitting, or ion-exchange related—are driven by chemical or geometric factors rather than microbial activity, so they aren’t prevented primarily by cleaning and biocides in the same way MIC is.