Surface Charge Considerations in the Pitting of Ion‐Implanted Aluminum

The relationship between the pitting potential of an oxide‐covered metal, and the p H of zero charge of its oxide, , was studied by ion implanting aluminum (99.999% purity) with elements whose oxides were of known (Mg, Al, Si, Cr, Zr, Nb, Mo, and Zn). The results showed that all the implants chosen because of the low of their oxides (Si, Cr, Zr, Nb, and Mo) produced binary surface alloys that had higher (more positive) pitting potentials than aluminum. The implants chosen because of the high of their oxides (Zn and Mg) produced binary surface alloys that had pitting potentials that were either lower than (Zn) or the same as (Mg) that of aluminum. The Mg‐Al surface alloy results are explained by selective leaching of the Mg from the oxide. The implantation of aluminum into aluminum had no effect on the pitting potential, indicating that the increased and decreased pitting potentials observed for the other implants was a chemical effect.