Atmospheric corrosion of Zn and Zn alloys with local NaCl contaminations was studied in situ by scanning Kelvin probe. The corrosion process was accompanied by the formation of clearly separated anodic and cathodic locations and local galvanic cells on the surface. The corrosion activity correlated to variations in Volta potential during air to nitrogen transients. The effect of dielectric and semiconducting solids on the efficiency of cathodic reaction on zinc was investigated. The rate of oxygen reduction was high on semiconducting ZnO films with defective structure, as they are effective donors of electrons. Mg, Ti, Cr, and Al were alloyed to zinc to modify the composition of surface oxide films. The addition of Mg provided the most effective corrosion inhibition, blocking completely the spreading of the cathodic area from NaCl contamination. The other elements had minor influence, but might be applied for further improvement of the Zn-Mg system. The effect of Mg is believed to be connected to semiconducting properties of the formed surface oxide film.