THE WETTABILITY OF INDUSTRIAL SURFACES - CONTACT-ANGLE MEASUREMENTS AND THERMODYNAMIC ANALYSIS

The water wettability of surfaces, whose surface conditions are comparable to those used in heat and mass transfer equipment, has been investigated experimentally and theoretically. Results of contact angle measurements for water on metal and non-metal surfaces are reported. With hydrophobic non-metal surfaces (e. g. Teflon) water forms large advancing and receding contact angles, and the contact angle hysteresis is small. A thermodynamic analysis of the wetting of heterogeneous surfaces is presented. Equilibrium considerations for a model surface consisting of two components of different wettability provide the advancing and receding contact angles for a heterogeneous surface as a function of the equilibrium contact angles, surface fractions, and the distribution function of the two components. The results of the model calculations give a physically based explanation for the characteristic wetting behaviour of industrial surfaces found experimentally.