Since over 20 years it is known that riblet surfaces can reduce drag in fluids. The process by applying riblet paint in a single step by application, embossing and partial curing by UV-light is an alternative to bonded riblet foils for large area applications. The main advantage of this technique is the ability to paint three-dimensional surfaces with a functional riblet surface without any additional process steps, thus ultimately saving costs. This publication demonstrates the process insensitivity to different levels of compression, as resulting for example from non-planar 3d-surfaces. Additionally, the performance of the process was investigated in terms of maximum application speed, and the quality of the coating at those speeds. The results outline the advantages, and limits, of this application technique, and give an overview of the current process abilities of the coating process

The installation of offshore wind turbines has achieved rapid and substantial progress worldwide and further increase is predicted by enhanced technologies that will reduce costs and increase service time. Secondary structures applied to the primary structure, as the transition piece of a monopole, can be e.g. cable support, boat landing or anode systems. These structures are often welded, which leads to problematic notch effects and hydrogen embrittlement, especially for underwater applications. Also the handling of technical equipment as power current or artificial housings for scuba divers for underwater welding is challenging. Adhesive bonding will lead to cost reduction as the mentioned negative aspects can be avoided. The corrosion protection coating and the primary structure will no longer be damaged and therefore do not need a subsequent coating. This article focuses on the area which is permanently exposed to water. A critical point is how the capability to form adhesion and cohesion, will be influenced by the application process under water. Therefore, stud bonding fasteners are designed that enable the injection of adhesive to the bonding area under water. The load capacities for different adhesives, surface pre-treatments and the degradation by exposure to artificial sea water were investigated. Adhesion was achieved with two different adhesives, which were able to cure and realize reasonable strength under water. Furthermore, two selected coating systems were able to improve the perfor-mance of the adhesive bond.

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