Impact of climate change on long-term corrosion of offshore wind turbine monopiles

Offshore steel structures are subjected to deteriorating environmental actions affecting their performance and structural reliability. Marine corrosion is recognized as a leading factor reducing service life and reliability of offshore wind turbine (OWT) monopiles. This paper evaluates the influence of corrosion on the structural performance and reliability of OWTs’ monopile using a bi-modal corrosion model. The impact of sea-water temperature in changing climate on corrosion loss is investigated. Corrosion loss and its associated uncertainty are evaluated for various sea-water temperatures corresponding to different wind farms to investigate the impact of OWTs’ location on corrosion deterioration. Three scenarios for applying climate change effects are considered to investigate the impact of global warming using the projections provided by Intergovernmental Panel on Climate Change (IPCC). Reductions in the OWT’s cross-sectional properties and structural reliability due to corrosion in different climate conditions are estimated for a monopile geometry representative of the NREL 5 MW OWT monopile. To evaluate structural safety in the presence of corrosion, reliability of corroding monopiles which have been designed using partial safety factors specified by IEC 61400–1 (edition 4) are assessed for multiple extreme design load cases. Results show that baseline sea-water temperature substantially influences corrosion loss, which differs by up to 40% among the investigated locations. This difference is significantly greater than the 1.5–1.7% increase caused by climate-change-induced warming at a given location. Corrosion reduces the annual reliability index by up to 15%, whereas the adopted warming scenarios have a negligible effect on reliability. Thus, for the model and scenarios considered here, site-specific baseline temperature and corrosion deterioration are more influential over the 25-year service life.