Development of ice protective surfaces via reduction of surface roughness

Ice protective coatings present an opportunity to replace traditional ice protection systems which not only have large power and weight requirements but also increase complexity of the vehicle design. A major issue with many coatings is durability. This paper explores whether robust surfaces such as stainless steel and titanium aluminum nitride (TiAlN) coatings can be made ice protective by decreasing surface roughness. Impact ice adhesion strength testing was conducted using the Pennsylvania State University’s Adverse Environment Rotor Test Stand facility. Tests were conducted on stainless steel with surface roughness values of 10 to 80 nanometers and on TiAlN coatings with surface roughness values of 42-62 nanometers. The test results showed that stainless steel surfaces could be made ice protective by modifying only the surface roughness. Stainless steel surfaces with a roughness of 10 nanometers were found to have an ice adhesion strength of 13.8 kPa (2 psi) at-8^◦ C. TiAlN coatings have not yet been made ice protective. Coatings with a surface roughness of 53 nanometers were found to have an ice adhesion strength of 41.28 kPa (6.99 psi) at-8^◦ C. A general trend was seen that showed ice adhesion strength decreased as the surfaces become smoother. A key finding of the research showed a reverse in this trend for smooth TiAlN coatings. Further investigation revealed the coatings contained pin holes which are believed to significantly affect ice adhesion strength. Developing a solution for removing the pin holes will be key to further reducing the ice adhesion strength of TiAlN coatings.