The economic use of offshore wind turbines requires a reliable and long-lasting corrosion protection. Sophisticated multilayer coating systems consisting of a thermal spray coating – mainly ZnAl15, a sealer and several layers of organic coating – have been proven to provide such protection. Damages to these duplex-coatings can, however, not be prevented necessitating on-site repair. In case of severe damages, the remaining coating close to the damage is often removed and subsequently, the duplex coating is rebuilt from scratch. In the present study, two integrated coating removal and substrate pre-treatment methods are investigated. For this purpose, duplex-systems were produced, artificially damaged by milling and afterwards treated by either grit blasting or with a rotating steel-wire brush, i.e. a Monti Bristle Blaster. Afterwards, the duplex coating was re-applied in the considered area. To evaluate the influence of the pre-treatment method on the coatings’ corrosion protection potential, a 38 week-long salt spray test was used. The test revealed a pronounced influence of the pre-treatment method on the corrosion protection potential. In case of grit blasting, no substrate corrosion could be detected. The use of a Bristle Blaster, however, resulted in coating failure and some spots of red rust.

At present, main bearings in wind turbines are equipped with rolling bearings without exception. Sliding bearings instead can offer a number of advantages, including easier maintenance and extended lifetime. While conventional manufacturing processes for large sliding bearings face their limits regarding processable materials, thermal spraying can provide an effective alternative to meet the requirements by applying coating systems on the bearing surfaces. Within this study a wide range of different feedstock materials based on standard bearing materials and common wear and friction reducing coating systems are investigated. The coatings are tested on tribometers based on the load distribution within the main bearing at critical operating conditions of the wind turbine gained from a validated simulation model. A tribological methodology is developed to investigate the application related properties of the thermally sprayed coatings. The effects of load and geometry of the counter body on the friction and wear behavior of the coatings are investigated using a pin-on-disc and a modified high-load ring-on-disc tribometer. The presented results provide a major contribution to the purpose of identifying an appropriate coating system to meet the requirements of slow-moving and highly loaded sliding bearings.