Publications Details
Correlating pit initiation in aluminum with passive oxide defect structure
Microelectrochemical methods are combined with scanning electron microscopy to explore passive oxide breakdown and pit initiation on Al(111) thin films. Anodic galvanostatic polarization is conducted in a microcapillary cell to limit the available current and to restrict the analysis area for subsequent microscopic evaluation. An ability to drive a single pit initiation event is demonstrated using this approach. Subsequent microscopy shows that pore cluster formation on the off-(111) axis facets that are emergent from the grain boundaries is responsible for pit initiation. Early stage, fully formed pits possess oxide membranes that contain pore clusters. Pores evolve from voids that form at the oxide-Al interface, establishing a link between these interfacial voids and pit initiation. Localized oxygen vacancy saturation and the anion-cation vacancy annihilation reaction during anodic polarization drive void growth, the void-to-pore transition, and pit initiation at off-(111) axis facets in this system. ©The Electrochemical Society.