Protecting compression springs effectively

In order to counteract the weight force when using liftgates, pre-tensioned compression springs are used in automotive construction. Due to their length-to-diameter ratio, these are not resistant to bending. This makes it necessary to run the spring internally and/or externally in plastic or metal tubes. When the liftgate opens and closes, there is therefore local bearing and relative movement between individual coil segments and the guide elements. This can result not only in noise, but also in wear - up to and including corrosion and spring fractures. These consequences are effectively avoided by using the DÖRKEN coating system on the spring.

Metal surfaces that rub against each other - especially under cyclical continuous load - pose a great challenge for coatings. A system with a multi-layer structure provides a solution in such cases: The steel is first coated with a 7 to 10 µm thick zinc flake coating. On top of this, a highly cross-linked organic coating based on epoxy or PU is applied, ideally filled with tribologically active ingredients such as PTFE. PTFE-free lubrication is also possible at this point. In order to ensure that the coating remains resistant to permanent stress, the use of a plastically deformable wax-based lubricating layer is also essential. An admixture of particulate lubricants as spacers offers advantages here as welle.