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Coating has been recently considered as having good potential for use in preventing in-cloud icing on the leading edge of the lifting surfaces of an aircraft in cold climates. In terms of wettability, a coat may exhibit hydrophobicity or hydrophilicity depending on its specific properties. The same applies to the ice adhesion strength, which may be either high or low. It is thus necessary to determine which type of anti-icing or de-icing coat would be appropriate for a particular application in order to fully utilize its specific properties. Notwithstanding, a coat is incapable of preventing ice accretion by itself, and a perfect icephobic coat is yet to be developed. Coating is also sometimes applied to the surfaces of electrical heaters and load-applying machines to enable them to function more effectively and use less energy. The coating used for an electric heater, for instance, should be hydrophobic because of the need for rapid removal of molten water from the surface.

Unlike the conventional bleed-air method, using electro-thermal anti-/de-icing methods to completely evaporate all of the supercooled water droplets that collide with the leading edge wing surface of aircraft flying in a freezing environment is not easy in terms of technical feasibility and energy efficiency[1]. If the leading edge is warm enough to stay free from frozen water droplets, the water moves backward while still maintaining the liquid phase. The droplets may freeze somewhere on an unheated surface after being halted for some reason and stick on the surface. Ice gradually accumulates as this process is repeated. Therefore, liquid water must be removed from the surface as soon as possible if the electrothermal method is employed for icing prevention. One answer to this problem is coating the surface with a superhydrophobic paint.

An icing process of a single supercooled-water droplet is focused in the present study. A stationary icing as well as an icing of a moving droplet gives us great insights into the development of an ice-prevention system for engineering purpose. For academic purpose, it gives experimental findings in a two-phase flow. To understand the icing process, we applied a luminescent imaging technique. It uses a temperature-sensitive luminophore and a temperature-insensitive luminophore to create the luminescent water. The luminescent outputs from these luminophores are simultaneously captured by a high-speed color camera. By simply taking a ratio, the temperature distribution can be extracted. In this paper, this imaging system is shown with its temperature characterization. An icing process of a stationary droplet is shown in this paper. Also, a current status of an icing process of a moving droplet is shown.

Anti- or de-icing of an aircraft is necessary for a safe flight operation. Mechanical processes, such as heating and deicer boot, are widely used. Deicing fluids, such as ethylene glycol, are used to coat the aircraft. However, these should be coated every time before the take-off, since the fluids come off from the aircraft while cruising. We study a hydrophobic coating as an anti-icer for an aircraft. It is designed to coat on the aircraft without removal. Since a hydrophobic coating prevents water by reducing the surface energy, it would be an alternative to prevent ice on the aircraft. We provide a temperature-controlled room, which can control its temperature under icing conditions (-10 to 0 °C). The contact angle and the sliding angle are tested for various hydrophobic coatings. Candidate coatings are tested under super-cooled water spraying and under the representative in-flight icing conditions.

New icephobic paint has been developed for the purpose of preventing the icing of the airfoils of aircrafts. The basic characteristics of the paint in terms of icing prevention were examined by an optical method and a load test. The water contact angle is so high-150 degrees-that high water repellency can be obtained as expected from the design. The adhesion strength of the ice formed on this coating is decreased to the lowest value as compared to all paints ever developed. The results from the icing wind tunnel test carried out in conditions similar to what aircrafts encounter show that the paint contributes to fuel and weight savings due to the effective use of deicer.