Corrosion experiment installed on the seabed in the North Sea

On 8 and 9 October 2025, a unique corrosion experiment by Sirris was installed at Blue Accelerator maritime test platform off the coast of Ostend. The installation was carried out by divers from Antwerp Underwater Solutions, using a vessel provided by Ostend Marine Services. The setup – possibly the first of its kind – aims to study how steel corrodes at the foundations of offshore wind turbines.

The area where the monopile enters the seabed is particularly critical. It experiences the highest bending loads, yet it is extremely difficult or even impossible to inspect. As a result, this so-called mudline zone remains largely unmonitored, and very little real-world data exists on corrosion processes at the seawater–sediment interface. Even scientific literature offers limited insights, especially regarding microbiologically induced corrosion (MIC) and pitting corrosion. This lack of understanding leads to uncertainty for wind farm operators about how corrosion affects the lifetime of their assets.

Understanding corrosion at the seabed

The goal of this experiment is to improve understanding of corrosion behaviour at the transition between seawater and seabed, and to test state-of-the-art corrosion sensors that can continuously monitor this hidden process. The data collected will help refine maintenance strategies and reduce inspection costs.

A custom-designed frame was installed on the monopile structure of Blue Accelerator, located about one kilometre offshore. The platform, managed by POM West Flanders, serves as a maritime innovation and demonstration site under real offshore conditions.

Inside the frame, built and installed by Antwerp Underwater Solutions, two steel pipes were placed — each 2.5 metres long and 193.7 mm in diameter. The first pipe was installed in April, reaching 10–20 cm below the seabed. The second was added in October using an improved installation method, reaching a depth of 40–50 cm. This second pipe now houses corrosion sensors developed by C-CUBE and MetriCorr, which are currently monitoring in-situ corrosion at the seabed.

Analysis in 2026

In summer 2026, the frame, pipes and sensors will be retrieved for detailed analysis. Researchers will then assess the corrosion that occurred and use the findings to refine future tests. The results will provide valuable insights into mudline corrosion in the Belgian part of the North Sea and help offshore wind operators better model and predict the lifetime of monopile foundations.

This research is partly funded by the Horizon Europe WILLOW project and made possible through the expertise and support of Ostend Marine Services (Brabo, vessel), Antwerp Underwater Solutions (diving team and frame), Hypertechnics (underwater housing for the data system), C-CUBE and MetriCorr (corrosion sensors), and access to Blue Accelerator test site coordinated by POM West Flanders.