Cor­ro­sion pro­tec­tion at the heart of the wind en­ergy unit

The components fitted to wind energy units are large in size and are subjected to very high levels of climatic and mechanical stress. Effective corrosion resistance is therefore all the more important. But how should this be applied to the large components and subsequently dried? Simple: with solutions that cure at room temperature!

Component protection required

Wind energy units and the parts that they contain are subjected to numerous environmental stresses every day, together with constant static and dynamic loads. The components of the units are required to resist these stresses and function smoothly at all times, even when subjected to rain, salt water, heat, cold and UV radiation. If individual components fail, for example due to corrosion, this means costly downtime for maintenance or repair work. As a result, components need to remain operational as long as possible. This is also the case for the roller bearings installed in the area of the rotor. They have an elemental influence on the function of the unit as a whole and need to satisfy the highest requirements with regard to load transfer, efficiency and reliability.

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Components fitted to wind energy units are subjected to numerous extreme stresses and therefore require high-performance corrosion protection.

Coating large components – but how?

In practice, high-performance zinc flake systems have proven to be the most economical and enduringly reliable corrosion protection solution. These consist of a basecoat and matching topcoat, achieving a high active cathodic protective effect even at very thin coat thicknesses of 8–20 μm. This enables zinc flake systems to fulfil the high requirements of the wind energy unit manufacturers – such as very long corrosion durability without rust formation and enhanced UV resistance. One particular challenge when coating complex, large components for wind energy units is the application process. As components such as brake discs and roller bearings are very solid and can reach diameters of over one metre, these no longer fit in the classic drying ovens after coating. DÖRKEN has solved this problem with zinc flake coatings that cure at room temperature.

Room temperature curing zinc flake system from the spray can

The room temperature curing basecoat developed by DÖRKEN is especially suitable for large, solid or temperature-sensitive components. Application occurs using standard spray processes such as HVLP, Airmix or high-speed atomisation. This involves the parts being coated with an even coat of paint using the rack procedure. The decisive advantage: as the zinc flake coating cures rapidly and completely at room temperature, no subsequent annealing in the furnace is required. At a temperature of 20 to 25°C the coated component cures within approximately 60 minutes. If the process is forced – for example at 80°C – curing within 10 minutes is possible. In addition, no hydrogen is generated in the coating process and there is therefore no risk of hydrogen-induced stress corrosion cracking. The room temperature curing basecoat enables a high-performance corrosion protection of 1,440 hours as per neutral salt spray testing (DIN EN ISO 9227) and condensed water testing according to DIN EN ISO 6270-1 (with 1 mm scoring) to be achieved. Subsequent sealing with a topcoat is recommended for an optimal protective effect.

Zinc flake coating from the spray can

n addition, Dörken also offers a room temperature-curing zinc flake coating from the spray can. This basecoat is also chromium VI-free and adheres very well, it is especially suited to the improvement of missing areas following the coating and treatment process, as well as the coating of small areas of component groups that are already in place. The coating cures at room temperature after approximately 20 minutes and fulfils the high requirements of condensed water testing and salt spray testing according to DIN EN ISO 9227.