Fasteners in an increasing number of applications demand high functional safety. They transmit ever higher forces despite highly optimized cross-sections. In addition, the design is often based on the service life of the component. In this respect, the coating of the screws plays a key role, especially when it is also necessary to withstand extreme weathering. Due to their particularly reliable corrosion protection despite low coating thicknesses, fastener manufacturer EJOT also uses zinc flake coatings in many projects. The organic coating systems with zinc-aluminum flakes offer very high corrosion protection without any risk of hydrogen ingress that could weaken the material.
However, application process for zinc flake coating is not trivial. With commercially available processes, the coating medium may not be cleanly displaced during the spin-off process, leaving residues on critical areas such as drives. Especially with an internal force application and small diameters this can lead to the fact that the tool cannot be inserted easily enough or even deep enough. Therefore, EJOT relies on a newly developed centrifugal technology at the production site in Tambach-Dietharz, which achieves a particularly even and thin layer structure even with very small screws. As a result, even small, complicated parts up to bit sizes of T6 or IP6 can be coated with process reliability. With conventional processes, there was a limit here ≥ T20. As a corrosion expert, Dörken supplies the component-specific coating material and was also involved in the planning process for the project.
The result of the last five years of cooperation with the plant manufacturer WMV is impressive: Together, a component-specific coating was found and the world's first system was developed that can coat 120 kg of material with positional change at 32 g acceleration. The patent-pending WMV PULZ system (planetary circulation coating centrifuge) is used, among other things, to coat very small parts with hollow bodies and screws. Due to the permanent circulation with simultaneous high acceleration value (32g), the parts are coated evenly, reliably and with a thin layer. This also benefits the environment, as this optimized coating process can reduce CO2 emissions by around 30 percent compared to previous processes.