High-purity aluminum samples were implanted with 35 keV Cl+ then polarized in both Cl-- containing and Cl-- free electrolytes in order to ascertain corrosion behavior as a function of Cl- content in the oxide. Implant fluence between 5 x 10(15) and 2 x 10(16) Cl+ cm(-2) resulted in little or no localized attack. Implant fluences of 3 x 10(16) and 5 x 10(16) Cl+ cm(-2) resulted in significant pitting in a Cl-- free electrolyte with the severity scaling as a function of implant fluence. The low variability in the pitting behavior of the 5 x 10(16) Cl+ cm(-2) sample suggests that this implant dosage results in a critical Cl- concentration in the oxide for pit nucleation. The passive current density (i(pass)) decreased with increasing implant fluence. A space-charge effect is proposed to account for this phenomenon, although effects from defect interactions and possible oxide thickening are still under consideration. (C) 2004 The Electrochemical Society.