Localized Corrosion of Al-Based Amorphous-Nanocrystalline Alloys with Solute-Lean Nanocrystals: Pit Stabilization

Abstract

The localized corrosion resistance of several partially nanocrystalline Al-based metallic glasses was examined in fully amorphous, partially nanocrystalline, and fully crystalline microstructures. In all of the alloys examined, , , , and , the pitting potential remained elevated relative to pure Al in all partially nanocrystalline states. The pit growth kinetics of the alloys, which were examined using an artificial pit technique, showed that the anodic kinetics were ennobled and the cathodic kinetics were faster than those of pure Al. The pit stability product was also found to be lower for Al than for the fully amorphous alloys. Artificial pit growth experiments also showed that the difference in the repassivation potential between pure Al and the amorphous alloys is not due to the differences in the potential dependence of the transition to tunneling. There was no significant difference between the pit growth kinetics of the fully amorphous and partially nanocrystalline states of the alloys. Because the nanocrystals do not affect the growth kinetics of large ( radius) artificial pits, it is concluded that any effects nanocrystals have on the pitting resistance of alloys must be related to pit initiation or early growth.