A Study of Localized Corrosion in Al Resulting From The Controlled Introduction of Cl

High purity Al samples were implanted with 35 keV Cl+ then polarized in Cl--free electrolyte in order to ascertain corrosion behavior as a function of Cl content. Electrochemical data indicated implant fluences between 5x1015 and 2x1016 Cl+cm-2 resulted in little or no localized attack. Implant fluences of 3x1016 and 5x1016 Cl+cm-2 resulted in significant attack with the severity scaling as a function of implant fluence. The low variability in the behavior of localized corrosion for the 5x1016 Cl+cm-2 sample suggests that this implant dosage may result in a critical Cl- in the sample for pit nucleation. Optical and Electron microscopy images indicated some reactivity associated with lower fluences (1x1016Cl+cm-2), possibly indicating enhanced general dissolution. At high magnification the corrosion was observed to occur outside the implanted boundary through mechanisms of tunneling or altered local chemistry at those sites. The SEM images reveal a form of localized corrosion with a crystalline character.