Microbiologically Influenced Corrosion Preliminary Study — Mornington Peninsula VIC

Project summary

iEnvi completed a preliminary study in March 2020 to assess the risk of microbiologically influenced corrosion (MIC) to planned pipeline assets and pipe prefabrication/staging areas on the Mornington Peninsula, Victoria. The work was completed in collaboration with technical specialists from Swinburne University.

What is MIC?

Microbiologically Influenced Corrosion (MIC) describes changes in corrosion behaviour caused by microorganisms (bacteria, yeast, fungi) and their metabolic products. The most common consequence is accelerated, localised corrosion such as pitting, which can significantly shorten asset life if unrecognised.

Why this matters for pipeline projects

• Localised pitting from MIC can cause unexpected pipeline failures, service interruptions and expensive replacements.
• MIC-related failures can increase construction, maintenance and insurance costs and may affect approvals and developer liability.
• Early identification allows cost-effective mitigation (material selection, coatings, cathodic protection, soil treatment and targeted monitoring).

Investigation approach

The preliminary study combined a desktop review of existing environmental reports (including soil moisture and rainfall patterns) with a targeted field sampling program. Key elements:

• Soil samples collected at 0.1 m and 0.5 m below ground surface at pipeline alignments and staging areas.
• Laboratory Biological Activity Reaction Test (BART™) analyses and standard corrosivity parameters.
• Field pH testing using pHF and pHFOX methods and laboratory analysis for physicochemical corrosivity factors and potential acid sulfate soils (PASS).
• Technical input and interpretation with Swinburne University MIC specialists.

Key findings

• Laboratory and field results indicated the presence of three microbial groups commonly associated with MIC: sulfate-reducing bacteria (SRB), acid-producing bacteria (APB) and iron-related bacteria (IRB).
• Physicochemical indicators (including pH and parameters used to screen for PASS) were assessed alongside the microbiological results to separate biological from abiotic corrosion drivers.
• On the balance of evidence from this preliminary program, MIC was identified as a credible risk to the proposed pipelines and handling areas.

Recommended next steps

Given the preliminary nature of the work, iEnvi recommended targeted follow-up to quantify risk and define mitigation:

• Detailed metallurgical testing and microbiological characterisation at representative locations (including quantitative SRB/APB/IRB enumeration and molecular assays where appropriate).
• Site-specific corrosion testing (coupons, probes or electrochemical tests) under anticipated in-service conditions.
• Material selection review, coating and cathodic protection specification, and construction sequencing to limit exposure during installation.
• Soil management and drainage controls where PASS or low-pH soils are present.
• Ongoing monitoring plan to detect early corrosion activity during operation.

Practical takeaways for developers and asset owners

• Addressing MIC risks during planning and procurement reduces the lifecycle cost of pipelines versus reactive remediation after failure.
• Targeted confirmatory testing is a relatively small upfront investment compared with potential replacement, downtime and liability costs.
• Combining microbiological and physicochemical data provides a defensible basis for specifying coatings, cathodic protection and maintenance schedules.

Notes on technical claims

Some cost estimates for global and national MIC impacts reported in industry literature vary; these figures should be independently verified where used to support financial decisions.

Contact iEnvi

If you have planned assets in potentially corrosive or acid sulfate soils, contact iEnvi to scope targeted MIC investigation and mitigation. Call us on 13000 43684 or visit /contact/.