Low cost corrosion protection for offshore wind

Corrosion is a top three failure mechanism for offshore wind energy farms. Due to poor accessibility of the offshore structures the costs for offshore operation and maintenance are at least 10 times higher (e.g. 5000,- to 6500,- Euro per square meter for offshore repairing of corrosion coating in the splash zone) compared to the costs for turbines on land. Therefore, in order to keep the maintenance costs low the corrosion protection should have the same lifetime as the turbine. A corroding structure will have a very short fatigue life, particularly if the welds are corroding. A reliable corrosion protection system is therefore of vital importance for the lifetime of the construction. The objective with this work has been to benchmark commercially available protective coatings, which was done using different laboratory tests and an offshore splash zone field test. The samples in the field test have only been exposed for 16 months so far, but already we can see very distinct differences between the various coating systems. The field test will continue until 5 years exposure. A thick film polyester coating is showing no sign of degradation, which correlates well with experiences from the oil and gas industry. Coating systems with thermally sprayed zinc (TSZ) are also performing excellent in the field test, including simplified coating systems with only one paint layer on top of the zinc. The performance of various epoxy based coatings varies. Correlation to the various laboratory tests vary, particularly for the TSZ based coating systems. The protection mechanism for these systems is somewhat different from the pure barrier coatings, which correlate excellently with lab tests.