Adsorption Effect on Wetting in a Copper/Lead System

Complex analysis of interfacial thermodynamics was performed for a lead–copper binary system. Contact angle on polycrystalline copper and surface tension was measured for saturated Pb–Cu alloys at 390–1000 and 390–800 °C temperature ranges correspondingly. Liquid–gas and interfacial solid–liquid energies were calculated for Pb–Cu binary system by statistical thermodynamics on the basis of regular solution approximation at 390–950 °C. Calculated values coincide well with measured ones and with literature data, except for the temperature region lower than 700 °C, where the reported values of interfacial energy seem to be overestimated. Analysis of literature data leads us to the conclusion that an adsorbed monolayer film of lead exists in equilibrium with Pb–Cu drop on copper/gas interface between 250 and 900 °C. The decrease of the solid/gas surface energy due to Pb adsorption was calculated on the basis of the Young equation and fitted with the Szyszkowski equation. An adsorption energy of 276 kJ/mol and a vibration period of 2.79 × 10–14 s–1 were found.