Review of corrosion fatigue in offshore structures: present status and challenges in the offshore wind sector

Offshore wind has been identified as one of the emerging sustainable energy sources in the United Kingdom. Offshore wind turbine support structures are mainly fabricated of welded tubular members, similar to structures used for oil and gas applications, and are exposed to highly dynamic, harsh marine environments. However, their structural details and design requirements are significantly different due to the magnitude and frequency of operational and environmental loadings acting on the support structures. These conditions would significantly affect their structural dynamic response characteristics due to the magnitude of the applied load. This may therefore have some significant effects on the crack growth behaviour and the extent to which corrosion can be associated with damage to the support structures. However, the magnitude of the applied load might depend on turbine size, water depth, soil conditions and type of support structures. It is therefore essential to design wind turbine support structures against prescribed limit states to ensure economical and safe operation. This paper presents a review of corrosion fatigue in offshore structures as regards the effects of seawater, environment and mechanical loading. Existing literature which documents results from previous campaigns is presented, including works referring to oil and gas structures, highlighting the significant difference in the aspects of loading and use of modern fabrication processes, with a view to illustrating the requirements for an update to the existing corrosion fatigue database that will suit offshore wind structures' design requirements.