The qualitative and quantitative characterization with Auger Electron Spectroscopy (AES) at the surfaces of bulk brass alloys with different stoichiometry have been carried out. In order to draw out a calibration curve to correlate the measured Auger signals to the true concentrations, the effects of ion bombardment on the surface composition (preferential sputtering) have been studied. The investigation has been performed in a concentration range from 60 to 100%at in Cu. The Auger measurements on clean surfaces have been executed on the alloys surfaces prepared in situ both by scraping and by sputtering with Ar ions. The results show that Zn is preferentially sputtered from the surface respect to Cu.