Study: Hydrophobic Coatings for Aircraft Deicing
A research team from the Skolkovo Institute of Science and Technology (Skoltech) in Moscow recently tested hydrophobic coatings and their effectiveness combined with other anti-icing systems.
Anti-icing fluids are typically applied to aircraft prior to takeoff, but can wear off quickly during acceleration. In-flight, aircrafts can use heaters and inflatable protectors against ice. Permanent hydrophobic coatings can also reduce wettability and do not allow water to freeze on the aluminum body but have previously been shown to render these anti-icing fluids less effective.
A recent study conducted by Canadian scientists suggested that anti-icing fluid might be prevented from creating a protective film when used with water-repellent hydrophobic coatings. Researchers at Skoltech then decided to test the surface wettability of aluminum in aircraft skin and see if it affects the performance of these fluids.
Three different types of fluids, which satisfied aerospace standards SAE AMS1424 or AMS1428, were tested. Each fluid type, including Type I, II and IV had different endurance times. Aluminum plates were sanded, polished and coated with a hydrophilic transparent, glossy or matte acrylic varnish.
In contrast to the Canadian team’s findings, they discovered that plate wettability had no impact on the performance of anti-icing fluids, but attribute this finding to the surface tension and viscosity of anti-icing fluids. Researchers also noted that surface roughness could play a role, since rough surfaces take longer to accumulate ice.
According to Skoltech, the study showed that the accumulation of liquid in the surface texture reduces the water-repellent properties of hydrophobic coatings.
“We think smooth hydrophobic coatings are better than rough superhydrophobic coatings when it comes to treatment with anti-icing fluids,” Viktor Grishaev, PhD, a senior research scientist at Skoltech and RSF grant project manager, commented.
According to the release, the research was supported by the Russian Science Foundation (RSF) Presidential Program grant and was published in International Communications in Heat and Mass Transfer. The full study can be read here.
Recent Icephobic Coatings
In November, Zentek Ltd., a Canadian development and commercialization company, announced the development of a new carbon-based, nanotechnology-enhanced icephobic coating.
Tests for adhesion strength required to dislodge ice from surfaces were conducted with a third-party lab, with the coating reportedly demonstrating an adhesion strength consistently around 20 kilopascals. ZEN reports that the typical ice adhesion strength of a bare aluminum alloy is about 500 kilopascals, while a classified icephobic surface must be less than 100 kilopascals, with the coating having a 96% improvement over aluminum and 80% improvement over the 100 kPa threshold.
“We continue to actively develop new nanotechnology-enabled applications in high-impact areas, which, in this case, has the potential to significantly increase safety for vehicles such as drones, aircraft, ocean vessels, wind turbines and other applications where, in cold weather climates, there is the potential for ice to accrete on surfaces, causing hazardous breakdowns in function,” said Greg Fenton, ZEN CEO, at the time.
“Our mission continues to be to develop innovative nanotechnologies that improve people’s lives – and while our focus is primarily on nanotechnology-enabled healthcare solutions – we are also making breakthroughs that substantially contribute in other industries that may result in vital steps forward to ensure public safety and enhance sustainability.”
ZEN plans to include this coating, which includes graphene, in flight testing under real world ice-forming weather conditions this winter, as well as testing if the coating is an effective passive method to de-ice drone propellers to fly safely in all-weather operations.
According to the release, the company filed a provisional patent for the technology in August with the United States Patent and Trademark Office and has begun to explore partnership opportunities.