CONTACT-ANGLE TEMPERATURE-DEPENDENCE FOR WATER DROPLETS ON PRACTICAL ALUMINUM SURFACES

zThis paper presents an experimental investigation of the temperature dependence of the quasistatic advancing contact angle of water on an a luminum surface polished in accordance with surface preparation techni ques commonly employed in boiling heat transfer studies. The surface, speculated to contain aluminum oxide and organic residue left behind f rom the polishing process, was characterized with scanning electron mi croscopy, surface contact profilometry, and ellipsometry. By utilizing a pressure vessel to raise the liquid saturation temperature, contact angles were measured with the sessile drop technique for surface temp eratures ranging from 25 to 170 degrees C and pressures from 101.3 to 827.4 kPa, Two distinct temperature-dependent regimes were observed. I n the lower temperature regime, below 120 degrees C, a relatively cons tant contact angle of 90 degrees was observed. In the high temperature regime, above 120 degrees C, the contact angle decreased in a fairly linear manner. Empirical correlations were developed to describe this behavior which emulated previous experimental data for nonmetallic sur faces as well as theoretical trends. Copyright (C) 1996 Elsevier Scien ce Ltd.