The surface of brass has been characterized by combined experimental and theoretical approaches. The experimental scanning tunneling microscopy study performed on a Cu0.7Zn0.3(111) surface at room temperature showed terraces of up to several tens of nanometers in width, separated by monoatomic steps. Depending on the tunneling conditions, a disordered pattern or a sharp atomically-resolved hexagonal lattice was observed. The disordered pattern is attributed to the superposition of Friedel oscillations at the surface induced by the presence of Zn atoms. Comparison of simulated images, based on a simple model of randomly distributed point defects, shows a good agreement with experimental results. At atomic resolution, a chemical contrast has been demonstrated between Zn and Cu atoms at the surface showing the random distribution of isolated Zn atoms into the hexagonal lattice.