The effects of alloying elements on the pitting corrosion of aluminum in an 1N–NaCl solution have been studied by using binary aluminum alloys containing different amounts of alloying elements, Fe, Si, Cu, Mg, Mn, Ni, V, Cr, B, Zr, Ti and Be. Anodic and cathodic polarization curves, pitting potentials, pitting dissolution currents and densities of pits at constant potentials were measured in the solution, and relations between the corrosion resistance and these properties of the alloys were considered. For increasing the resistance of the alloys against pitting corrosion, it was effective to add the elements which serve to increase the cathodic polarization. This is because the dissolution rate of the alloys in the immersion corrosion test was dependent upon the degree of cathodic polarization and independent of the anodic dissolution rate and the pitting potential.