Microbially Induced Corrosion in Offshore Wind

Microbially induced corrosion, sometimes called microbiologically influenced corrosion, happens when microbial communities on a metal surface change the local chemistry in ways that speed up corrosion. It is not a fringe concern in marine environments. It is a recognised mechanism that engineers design against in offshore oil and gas and, increasingly, offshore wind.

The key point for offshore wind is that the metal, the moisture and the microbes all coexist. Where a biofilm establishes on a steel surface in a damp, saline environment, the conditions for microbial corrosion processes are present. That does not make every biofilm a corrosion event, but it does mean microbial activity belongs in the asset-integrity conversation.

The clearest evidence comes from foundations. A 2025 in-situ study of microbially induced corrosion inside offshore wind monopiles found different microbial communities and corrosion behaviour at different depths. Steel specimens at around 6 metres were associated with iron-oxidising microbes, while specimens near 21 metres were associated with sulphate-reducing and methanogenic microbes.

That depth-dependent pattern is a useful reminder that microbial corrosion is not uniform and not hypothetical in offshore wind. It is measurable, it varies with conditions, and it is being studied in the field rather than only in the lab. For interiors, the honest read is that the same organisms and conditions are not automatically present, but the mechanism is real wherever moisture and microbes meet steel.

It would be easy, and wrong, to claim every patch of nacelle mould is proof of structural corrosion. The evidence does not support that leap, and overstating it damages credibility with the exact asset-integrity audience that matters. The careful position is better: recurring damp biological growth near coated or metallic surfaces is an asset-condition signal worth documenting, not a diagnosis of active corrosion.

That connects directly to how biological contamination should be handled inside a turbine. Mould and biofilm trap moisture against surfaces, and moisture against coated steel is the thing coating systems exist to prevent. Removing the biological load with a compatible product supports the corrosion-protection system rather than working against it.

The practical response is proportionate. Document biological growth properly, separate it from oil and salt residue, note where it recurs, and remove it with a product that is compatible with the coating system. That turns a vague housekeeping concern into evidence that can inform inspection and interval decisions.

It also means avoiding cleaning chemistry that trades one problem for another. A harsh product that removes biofilm but attacks the coating undermines the very corrosion protection you are trying to preserve, which is why coating compatibility sits alongside microbial control as part of the same asset-integrity picture.