Stephen Brown1, Jacques Lengaigne1, Navid Sharifi2, Ali Dolatabadi2, Ludvik Martinu1, Jolanta E. Klemberg-Sapieha1
1) Department of Engineering Physics, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada
2) Department of Mechanical and Industrial Engineering, Concordia University, 1455 de Maisonneuve Blvd. W, Montreal, Quebec H3G 1M8, Canada
In-flight aircraft icing occurs when supercooled water droplets suspended in clouds collide with exposed aircraft surfaces. The buildup of ice leads to increases in fuel consumption, decreases in lift and thrust, and in the worst-case scenario, accidents. In the worst case scenarios, icing can also cause the malfunction of sensors or moving parts, leading to accidents. Of the potential solutions which exist, superhydrophobic surfaces (SHS) are among the most promising, but are hampered by their often-low durability.
In the present study, we develop a thin-on-thick superhydrophobic coating system, focusing on the durability of the thin hydrophobic layer. The thick portion of the coating system is hierarchically rough TiO2, deposited by suspension plasma spraying, while the thin portion is a coating stack deposited by plasma enhanced chemical vapor deposition and is based on DLC:SiOx—diamond-like carbon networked with silicon oxide—selected for its improved mechanical properties compared to other hydrophobic coatings. The deposited DLC:SiOx films have a contact angle up to 95° and a hardness up to 11 GPa, and the whole thin-on-thick system having a contact angle of 159° and a contact angle hysteresis of 3.8°. Durability of the coatings is first assessed through icing/deicing cycling; results are compared to TiO2 samples coated with stearic acid and fluoropolymer, as well as commercial superhydrophobic solutions. Following this, the most interesting coatings were subjected to rain erosion tests and accelerated aging tests. The thin-on-thick coating system is shown to offer superior durability, maintaining water droplet mobility after 170 icing/deicing cycles, resisting prolonged UV and high-temperature exposure, and offering a 300-times improvement over the stearic acid in rain erosion tests.