Protection of Offshore Wind Turbines Using Damage Tolerant, Thermally Sprayed Aluminium Coating
Coating systems based on Thermal Spray Aluminium (TSA) protect offshore wind steel structures by acting as sacrificial anodes. TSA has a higher galvanic activity in seawater than steel, providing cathodic protection even when damaged. Precipitation of calcareous deposits on the exposed steel decreases the cathodic area and hinders oxygen diffusion, providing additional protection. While short-term laboratory tests have shown the effectiveness of damaged TSA coatings with minor defects (1%-5%), uncertainty remains about their long-term durability, especially in the case of large defects. This thesis introduces novel approaches that combine techniques and numerical simulations to comprehensively understand the performance of damaged TSA coatings in simulated marine environments and predict their expected lifetime in case of damage during service or installation. The optical analysis of sequential images captured in-situ provided a better understanding of the macro-phenomena related to the protective mechanisms offered by TSA in the presence of damage and their relation to potential changes. The multi-coupon electrode methodology separately evaluated the electrochemical behaviour in the defect and coated zones while maintaining the galvanic couple. These parameters were key inputs in the numerical simulation of the damage tolerance of TSA coatings. Hydrodynamic conditions significantly increased the corrosion rate of TSA and delayed the precipitation of deposits on the defect at least during the initial 10 days of exposure. The simulation predicted the protection provided by TSA and the corrosion rate as a function of the exposed steel surfaces, including the simultaneous effect of aluminium corrosion products and calcareous deposits formed in synthetic and natural seawater. These results, which align with existing data, have the potential to enhance the design of corrosion protection systems using TSA in offshore wind turbines. As a highly damage-tolerant coating, TSA could reduce human intervention and mitigate risks associated with offshore inspections and maintenance.
History
Supervisor(s)
Shiladitya Paul; Simon GillDate of award
2025-01-03Author affiliation
School of EngineeringAwarding institution
University of LeicesterQualification level
- Doctoral
Qualification name
- PhD