The stripping of the underpotential deposited (root 3x root3)R30 degrees sulfur lattice from Au(111) surfaces is studied by electrochemical techniques complemented with in situ scanning tunneling microscopy. The kinetics of the stripping process fits a model where adsorption/desorption competes with nucleation and growth of two-dimensional holes under charge transfer control. We propose that two phases compete for the electrode surface: a condensed phase consisting of holes nucleated at defects of the adsorbed layer and a diluted phase consisting of randomly distributed vacancies produced by desorption. The relative contribution of each process depends on the applied potential and the step density of the substrate.