Contact angle temperature dependence for water droplets on practical aluminum surfaces

Abstract

Abstract This paper presents an experimental investigation of the temperature dependence of the quasistatic advancing contact angle of water on an aluminum surface polished in accordance with surface preparation techniques commonly employed in boiling heat transfer studies. The surface, speculated to contain aluminum oxide and organic residue left behind from the polishing process, was characterized with scanning electron microscopy, 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 temperatures ranging from 25 to 170°C and pressures from 101.3 to 827.4 kPa. Two distinct temperature-dependent regimes were observed. In the lower temperature regime, below 120°C, a relatively constant contact angle of 90° was observed. In the high temperature regime, above 120°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 surfaces as well as theoretical trends.