Static- vs Impact-Ice-Shear Adhesion on Metals and a Self-Lubricating Icephobic Coating

To characterize the performance of icephobic coatings for aerospace applications, various shear-based techniques have been used. Generally, these techniques are conducted in conjunction with comparison tests on metals. In this study, a review of the various approaches for measuring adhesion for static and impact ice for metal and icephobic surfaces was done. This review indicated that many details of the test conditions either varied significantly among studies or were omitted. To address this uncertainty, new measurements were taken to examine in-situ ice-shear-adhesion strength for impact and static ice with various surfaces, using a consistent icing-research-tunnel facility with well-characterized and detailed test conditions. The results for the two different metals tested revealed a significantly higher ice adhesion for static ice compared to that for impact ice. However, the tested self-lubricated icephobic coating significantly reduced ice adhesion strength for both impact and static ice and this performance was retained after multiple icing tests. Based on the methodology review and the current experimental study results, it is recommended that future ice adhesion studies fully characterize the following: the apparatuses for shear measurement, which include protocols and procedures used; the surface chemistry and roughness; the thermal conditions of the air, water, and surface; and for impact ice, the droplet conditions such as velocity and size in order to ensure repeatability within a study and comparison across studies.