Microbiologically Influenced Corrosion (MIC) is a term that refers to the change (either acceleration or inhibition) in corrosion caused by the presence of microorganisms (bacteria, yeast, fungi), typically as a result of their metabolic activities. The most commonly known outcome of MIC is a dramatic acceleration in the rates of corrosion, typically in the form of localised pitting.
Corrosion of metal and other materials by microorganisms is a major problem worldwide and is estimated to cost as much as $30-50 billion per year in damage in the United States alone (Source). There was an estimated cost of MIC damage in Australia of AU$10 billion in 2016.
iEnvi was engaged by the client to complete a study to determine the risk of MIC to planned pipeline assets and staging areas where pre-fabrication of pipeline would occur. iEnvi collaborated with Swinburne University technical specialists in MIC corrosion.
A desktop review was undertaken of previous environmental investigations including soil moisture and rainfall patterns to identify if the conditions were suitable for MIC-related bacteria to thrive. Soil samples were collected from 0.1 and 0.5 m depth below ground surface in locations where pipeline was planned to be placed and staging areas, and submitted to a laboratory for Biological Activity Reaction Test (BART TM) and corrosivity parameters.
In addition, pHF and pHFOX field tests and laboratory analysis of physicochemical corrosivity factors were completed to determine the presence of potential acid sulfate soils (PASS) and non-biological corrosion risk factors.
Based on the desktop review, soil results and with the guidance of leading academics in MIC from Swinburne University of Technology, the risk of MIC was identified due to the presence of three microbial groups of bacteria related with MIC (sulfate-reducing bacteria (SRB), acid-producing bacteria (APB) and iron-related bacteria (IRB)).
Utilising the results from the preliminary study, iEnvi recommended further targeted investigations (metallurgical and microbiological) to determine the level of MIC risk more accurately, as well as preventative treatments to mitigate the onset of MIC.
The risk identification potentially would save millions of dollars in pipeline failure and replacement, and potential catastrophic failure.
If you have planned assets in acid sulfate soils, contact iEnvi to help investigate the potential for physicochemical and microbiological risk of corrosion at [email protected] or 1300 043 684 (13000 iEnvi).