Performance and wear tests of icephobic nanocoatings to prevent ice accretion on aerofoils

The accretion of ice on aircraft wings can disrupt aerodynamic control, lift characteristics and fuel efficiency in flight. In theory, the application of icephobic coatings should be effective in preventing the accretion of runback ice, formed from airborne supercooled droplets or from water generated by heating mats at the leading edge, as it is sheared back over the upper surface of the wing. The durability and the practicality of applying an icephobic coating to such a relatively large area have been prohibitive factors in developing this technology. In this study, the effect of temperature on the adhesion strength of ice was studied to determine optimum conditions and mould size for tests involving coatings. The ice adhesion strength of four coatings was then measured by shearing ice samples from coated plates by spinning them in a centrifuge. The durability of the coating performance was assessed by repeating the tests 17 times, regrowing ice samples on the previously used coatings. Contact angle parameters of each coating were tested prior to the first 10 tests to determine its influence on ice adhesion strength. The adhesion reduction factor, that is the ice adhesion to a coated plate relative to the uncoated equivalent, and coating wear rate were calculated to determine coating performance with repeat usage. Results indicate that contact angle hysteresis is a crucial parameter in determining icephobicity of a coating, and that hydrophobicity is not necessarily linked to icephobicity. Furthermore additional heat treatment during coating preparation, despite improving coating wear resistance, reduces initial and long term icephobicity.