Components in wind energy units are exposed to high climatic conditions as well as mechanical stress from wind force and the operation of the unit itself. To satisfy the high requirements and specifications of the plant manufacturers, each individual component needs to be protected against corrosion in accordance with the ambient conditions. Only in this way can cost-intensive maintenance work be reduced and plant lifetimes increased.

Exemplary components

Rotor blade fastenersFriction grip fittingsThreaded sleevesAnchor bolts (Onshore)

The rotor blades mounted in wind energy units are bound to the hub with fasteners, so-called expanding bolts and cross bolts. Typically, these are manufactured in thread dimensions M27 – M36 and strength class 10.9. As components subjected to heavy stress, they require long-lasting corrosion protection and must also be capable of being fastened securely and precisely.

Many of the plant components within the machine casing need to be fitted with high surface pressure due to the required level of mechanical stability. As a consequence, here too, fastening elements such as hexagonal bolts, threaded bolts, nuts or washers are utilised to join these components together with a high degree of material rigidity. Common dimensions here are from M20 to M64.

Threaded sleeves are the counterpart to expanding bolts or so-called double-end bolts. These are installed within the rotor blade or laminated. As maintenance work is extremely complex, long-lasting protection against corrosive influences is key here. Procedures have been developed for this that permit the partial coating of the threaded sleeves.

Anchor bolts are various types of bolts that are set into the foundation of the unit. The wind tower, for example, is secured to these up to 8-metre-long components – also known as foundation bolts. These components require complete or at least partial effective corrosion protection for the thread.


  • Corrosion protection (depending on use 1,000– 3,000 h as per DIN EN ISO 9227)
  • Customer-specific colouring
  • Defined coefficients of friction
  • UV resistance
  • Low maintenance & high economy


In wind energy units, the enormous stresses on components means that highly-effective zinc flake systems from DÖRKEN have proved their worth in practical use. The chromium(VI)-free coatings consist of a zinc flake base coat and an organic or inorganic topcoat. The high corrosion protection performance in combination with low coat thickness enables the coating of fastening elements in particular, with subsequent improvements in functional properties. This enables higher cathodic corrosion protection to be established. The application process does not involve the generation of hydrogen, with the result that there is no risk of application-related, hydrogen-induced stress corrosion cracking. The very thin, lubricated coats enable defined assembly – meaning that maintenance and assembly work can be carried out more easily and time efficiently.