Fluorescence and near-field scanning optical microscopy for investigating initiation of localized corrosion of Al 2024

The localized corrosion behavior of Al 2024 was investigated by using a fluorescent dye in combination with conventional fluorescence microscopy and near-field scanning optical microscopy. The fluorescent rings that mark the first steps of corrosion attack were associated with topographic features. The topographic rings were also observed in the absence of the dye, demonstrating that the observed rings are not artifacts. Anodic polarization in the absence of oxygen yielded fluorescent and topographic features similar to those observed under open-circuit conditions, indicating that the dye marks anodic sites. (C) 2000 The Electrochemical Society. S0013-4651(00)01-095-8. All rights reserved.