Prevention of Ice Accretion on Aluminum Surfaces by Enhancing Their Hydrophobic Properties

The accretion of ice on the surfaces of power network systems, aircraft, communication networks, etc., is known to cause serious problems that often lead to costly safety issues. An ideal solution would be to prevent ice from accumulating in the first place, rather than waiting for ice to accrete and then to de-ice which is both time-consuming and expensive. This may be accomplished by depositing coating materials that are icephobic. A low dielectric constant surface is expected to reduce the adhesion of ice due to the screening of mirror charges, thereby eliminating one of the strongest interaction forces-the electrostatic force of attraction-at the ice-surface interface. Superhydrophobic surfaces, which demonstrate high water-repellency due to the negligible contact area of water with these surfaces, are also expected to minimize the contact area of ice. In the present research work, both concepts were studied by producing superhydrophobic nanorough low-epsilon (dielectric) surfaces on aluminum. Superhydrophobic properties were achieved on surfaces of aluminum by creating a certain nanoroughness using a chemical etch followed by 'passivation' of the surface by a low surface energy coating of rf-sputtered Teflon, providing a water contact angle greater than 160 degrees. The same behavior is reported even when the nanorough substrates were coated with dielectric thin films of ZnO (lower epsilon) or TiO2 (higher epsilon) prior to passivation. It is found that the superhydrophobic nanorough low energy surfaces are also icephobic and the presence of a low dielectric constant surface coating of Teflon (epsilon = 2) allows a considerable reduction of the ice adhesion strength. Ice adhesion strengths were determined using a centrifugal ice adhesion test apparatus. (C) Koninklijke Brill NV, Leiden, 2011