EFFECTS OF OXIDATION AND SURFACE-ROUGHNESS ON CONTACT-ANGLE

Contact angle is known to be a parameter that affects boiling. This study was undertaken to measure contact angle of high and low surface tension fluids on copper and aluminum surfaces. Data were taken for polished, oxidized, and rough surfaces. A simple, yet fairly accurate method of measuring the static equilibrium contact angle of a solid/liquid interface is presented. The principles of a line light source and tilting plate were modified and then combined in the design of this apparatus. The angles obtained and their variation with the solid surface properties were in good agreement with previously published data. The contact angle of distilled water on a coarse copper surface was between 39-degrees and 72-degrees, while those of the organic fluids and refrigerants tested were in the range of 2-5-degrees. Roughness and oxidation reduce the contact angle. If the depth of the roughness is less than 0.5 mum, there will be no surface roughness effect on contact angle. The apparatus is fairly simple in construction, is inexpensive, and has good reproducibility. The measured angles were then compared to those measured with the sessile drop method.