The anodic polarization behavior of alloy Al–17Si–14Mg in borate solutions with and without 0.01 M NaCl was compared to that for pure Al. Results showed that, for the alloy, the passive current density increased but the pitting susceptibility decreased. The first effect was ascribed to a significant electrochemical activity of the Mg2Si intermetallics and the second to improved stability of the oxide film. X-ray photoelectron spectroscopy analysis of potentiostatically formed passive film on the alloy showed that it consisted of aluminum oxyhydroxide with incorporation of silicon in its elemental and two oxidized states (+3 and +4). Mott–Schottky analysis showed that trivalent silicon ion acted as an n-type dopant in the film. The interrelationship between passive film composition, electronic properties, and pitting behavior has been discussed.