# Parameter Study for the Ice Adhesion Centrifuge Test
## 2 Materials and Methods  
Material selection for this study was based on the results of a pre-screening process to identify robust and long-lasting surfaces that deliver reproducible results over the complete duration of tests. The preparation of test samples was performed in a single process with identical material batches to avoid deviations due to changes in the material composition, handling, or environmental conditions. Test samples (EN AW 5083, dimension 220 \(\times\) 30 \(\times\) 4 mm\({}^{3}\) for IFAM centrifuge tests) were sanded and cleaned with isopropanol prior to material application. For the first coating type, \"Primer\", an epoxy primer (Aerodur 37045 Barrier Primer White with Hardener S66/22R; Akzo Nobel, Sassenheim, The Netherlands), was used in a mixing ratio of 2:1 by volume. Material preparation and application were performed according to the supplier's specifications using a spray gun (SATA jet 90, 0.1.3 mm; pressure 1.6 Bar; distance 40 cm) under standard conditions (temperature 21 \({}^{\circ}\)C, relative humidity 40%). After the coating application, samples were stored at room temperature in a clean environment for 12 h prior to thermal curing at 60 \({}^{\circ}\)C for 60 min. The resulting dry film thickness of the primer was 40 \(\pm\) 10 \(\upmu\)m (according to DIN EN ISO 2808:2019 with byko-test 8500 P Fe/NFe, Byk Gardner, Geretsried, Germany) [18]. The second coating type, \"Standox\", is a clear coat that is used for repair purposes in the automotive industry. It was applied on the primer coating (described above) to ensure sufficient adhesion properties. Standocryl VOC-Premium Clear K9540 with Hardener VOC 10-20 was purchased (Standox GmbH, Wuppertal, Germany) and material preparation was performed according to the supplier's specifications at a mixing ratio of 3:1 (by volume). The application and curing parameters were identical to those of the primer coating. The same conditions were applied to the third coating type, \"PUR C25\", which is a non-commercial 2-component formulation based on silanized polyisocyanate-curing acrylic resin, as described in [16]. The material was selected as a potential icephobic material and was applied on the primer coating. The total film thickness (including primer) for the samples Standox and PUR C25 was 70 \(\pm\) 15 \(\upmu\)m [18]. The fourth material in this study was \"PTFE-tape\" (extruded polytetrafluoroethylene PTFE film tape 5490; 3M Deutschland GmbH, Neuss, Germany), which was applied on primed test samples according to the supplier's specifications. The film thickness of the tape was 90 \(\upmu\)m.  
All selected materials in the pre-tests showed sufficient mechanical and chemical resistance with no changes in the basic surface properties prior to and after repeated cleaning with isopropanol or during icing/de-icing cycles. Wettability tests were performed with the Drop Shape Analyzer DSA 100S (Kruss GmbH, Hamburg, Germany), according to relevant specifications (DIN EN ISO 19403-2) [19]. Surface free energy (SFE) was determined by measuring the dynamic contact angle of three liquids: water, diiodomethane, and ethylene glycol (droplet application of 0.2 \(\upmu\)L/s, total volume of 6.0 \(\upmu\)L), and calculated according to the method of Owens, Wendt, Rabel, and Kaelble (OWRK). The water contact angle (WCA) was extracted from this measurement. The water sliding angle (WSA) was determined with a water droplet volume of 20 \(\upmu\)L and tilting speed of 60 \({}^{\circ}\)/min. The sliding angle was defined as the angle at which the advancing and receding angles of the water droplet moved at least 1 mm from the starting point [20]. Contact angle hysteresis (CAH) was determined at this sliding angle or at the maximum tilting angle of 90\({}^{\circ}\) (in the case where the water droplet did not run off) by calculating the difference between advancing and receding angles. The tilting method was chosen as it delivers consistent results for fresh and aged coating surfaces.