Localized breakdown of passivity in commercial alloys typically is related to microstructural / chemical heterogeneities on the alloy surface. For instance, in stainless steels MnS inclusions are known to act as pit initiation sites. For Al alloys, many investigations have been carried out to study the role of different type of intermetallic particles in the pitting process. In our present work, we investigate different aspects of localized corrosion of Al alloys - examples include the role of grain boundaries in nanocrystalline alloys, influence of Sc on the pitting behavior of Al-Zn-Mg-Cu alloys, local electrochemical behavior of laser-beam welds in high-strength Al-Zn-Mg-Cu alloys. The presentation summarizes recent findings obtained by using microelectrochemical techniques, to understand the role of specific microstructural features in the localized corrosion behavior.