Localized attack on aluminum alloy 2024 in the presence of 0.1 M KCl was investigated using fluorescence microscopy. The study was conducted by high resolution confocal laser scanning microscopy in an in situ fluorescence mode. Fluorescein dye was used to indicate pH changes and surface chemistry over and around the active sites. Localized attack on Al was enhanced by the presence of inclusions and second-phase particles of different types. It was found that the fluorescence signal was confined to the surface due to the entrapment of fluorescein in the corrosion products formed on or around the inclusions.