Modification of hydrophobicity of metallic surfaces with an atmospheric plasma jet

Summary form only given. The ice formation in metal and polymer surfaces is a problem that affects many industries, such as aviation, refrigeration, energy, etc.; in order to diminish/reduce this issue, a technique to deposit hydrophobic coatings using atmospheric plasma has been developed. The atmospheric pressure reactors are easy to handle and to manipulate, and present one of the best alternative for surface modification without requiring a vacuum. The plasma is produced by a coaxial dielectric barrier discharge reactor operating with an inert carrier gas and a small amount of hexamethyldisiloxane (HMDS), which is the precursor for the coating which has been found to increase hydrophobicity on other materials. The end of the reactor has a conical shape in order to obtain a plasma jet. The reactor is made of quartz and is covered by an aluminum sleeve which serves as the anode; inside the reactor the cathode receives a high frequency and voltage feed. The samples were located in an XY motorized table for exposure; the variables of exposure time, distance to the source and electric power were modified in order to determine how those variables modified the properties of the surface, in particular the water contact angle, which is a qualitative measure of the coating hydrophobicity. To measure contact angle, drops between .5 μl to 1 μl were deposited on the modified substrate, and the system was observed with a microscope objective attached to a camera. The image was analyzed automatically with software to determine the contact angle. Results of exposure of aluminum surfaces raw, polished and painted with airplane grade paint were exposed and results of hydrophobic change are reported.