MIC Information: Biofilms

Biofilms are usually an essential part of the MIC process. Understanding how they work will help you undertand the damage that MIC can cause.


A biofilm is the start of a colony of different species of bacterium or a single species of bacterium:

Biofilms are aerobic on the outside & anaerobic on the inside. This allows for the formation of micro-environments that facilitate the growth of both types of bacteria.

The polymers created allow attachment points for additional bacteria and nutrients.

A mature biofilm creates tubercles (see Tubercles).

Where do biofilms form and why?

  • Welds – provide attachment points for bacteria
  • Threads – provide attachment points for bacteria
  • Where velocity is low – bacteria have time to attach
  • Where temperature is high – bacteria thrive at higher temperatures
  • Where nutrient level is high – bacteria grow at a faster rate with adequate nutrients
  • Where oxygen level is high – oxygen cell corrosion can jump start the MIC colonization process and aerobic bacteria thrive
  • Where oxygen level is low – anaerobic bacteria thrive here
  • Low spots in the system – sediments from the water settle here and provide nutrients and attachment points for bacteria
  • High spots in the system – air pockets can be trapped here and provide oxygen for oxygen cell corrosion and aerobic bacteria colonization

Are biofilms necessary for MIC?

Not always. Anaerobic bacteria can survive & function well in low oxygen conditions, such as wet ystems.

Only Pitting will be observed in such conditions.