Outdoor weathering study on Heligoland completed

In 2017 Dörken began an outdoor weathering study on Heligoland in collaboration with the Material Testing Laboratory (MPA) of the University of Stuttgart. The goal of the large-scale study was to characterise the corrosion protection performance of different coating systems and generate joint know-how. In addition to accelerated corrosion tests such as salt spray tests, outdoor weathering tests under realistic conditions are essential when it comes to estimating the performance of coating systems. In this case the challenge for the coatings lay in the maritime, highly-aggressive atmosphere on the island of Heligoland, with a particularly high level of salt content in the air. However, the particular circumstances of the test set-up, including travelling to the car-free island by ferry, made the project unique.

Different coating systems tested

Various components were exposed on Heligoland for a total of three years. Self-tapping screws were driven into sheet aluminium, wood screws into oak and spruce, to examine the effects of the respective wood types on corrosion. In addition, M10x80 bolts and sheet metal were exposed to the special environment. The parts were coated with diverse zinc flake coatings (DELTA®-TONE 9000, DELTA-PROTEKT® KL 100, DELTA-PROTEKT® KL 120) with different topcoats, the DELTA- PROZINC® electroplating system and a number of competitor products (zinc-nickel coating, hot-dip galvanization). The tests of the numerous coating systems and the subsequent knowledge of the extreme conditions gained mean that tailored recommendations can now be passed on to customers.

Samples are now analysed

The outdoor weathering study was concluded in June 2020, after three years. In the preceding years staff from Dörken and the University of Stuttgart travelled to Heligoland to view and document the corrosion process. At the end of the stress test samples were taken, to be analysed at the Material Testing Laboratory of the University of Stuttgart. The closing report is yet to be published.