The general assumption that metal vapors stick at any surface with probability one at room temperature is a necessary requirement for the correct metal deposition rate determination by quartz microbalance measurements. In a combined thermal desorption spectroscopy (TDS) and Auger electron spectroscopy (AES) study on clean and sulphur covered Pd(1 1 1) surfaces it is shown that Zn exhibits a reduced sticking coefficient on contaminated surfaces which violates the requirements for a proper application of a quartz microbalance. Additional CO titration and AES experiments were applied to calibrate the Zn coverage on Pd(1 1 1). (C) 2009 Elsevier B.V. All rights reserved.