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Tuesday, 24 September 2019
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Raw materials & technologies, Technologies

Researchers test protective coatings under offshore site conditions

Tuesday, 23 September 2014

Six corrosion protection systems for offshore wind power constructions were subjected to offshore conditions in the North Sea.

Special testing specimens were designed and manufactured and exposed to an offshore environment for three years. Source: Limnomar

Special testing specimens were designed and manufactured and exposed to an offshore environment for three years. Source: Limnomar

They have been subjected to offshore conditions on a test site in three different exposure zones, namely splash zone, intermediate zone, and underwater zone. The systems included single- and multiple-layered organic coatings, metal-spray coatings, and duplex coatings.

Coating integrity was satisfactory

Special testing specimens were designed and manufactured and exposed to an offshore environment for three years in order to characterise particular constructive details for different corrosivity zones. The following target parameters were investigated: intensity of fouling, anti-corrosive effect, coating adhesion, coating integrity, flange corrosion, coating performance over welds, and condition of screw connections. Fouling was an issue in the underwater zone and in the intermediate zone, but it did not affect the coating corrosion protection capacity. It was found that duplex systems, consisting of Zn/Al spray metallisation, intermediate particle-reinforced epoxy coating, and polyurethane top layer, provided the highest anti-corrosive effect. Mechanical damage to the coatings initiated coating delamination and substrate corrosion. Effective coating systems should be either very resistant to impact or able to compensate for corrosion of the steel. Flange connections were found to be critical structural parts in the splash zone in terms of corrosion. Notable crevice corrosion was observed at places. Except for one coating system, welds have been protected well. Welds, however, affected the corrosion of the steel inside the uncoated internal sections in the underwater samples. Coating integrity on difficult-to-coat structural parts was satisfactory for all systems.

The study is published in: Renewable Energy, Volume 74, February 2015, Pages 606-617.

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