CORROSION STUDY OF AA2024-T3 BY SCANNING KELVIN PROBE FORCE MICROSCOPY AND IN-SITU ATOMIC-FORCE MICROSCOPY SCRATCHING

The localized corrosion of AA2024-T3, and the behavior of intermetalli c particles in particular, were studied using different capabilities o f the atomic force microscope (AFM). The role of intermetallic particl es in determining the locations and rates of localized corrosion was d etermined using scanning Kelvin probe farce microscopy in air after ex posure to chloride solutions. Al-Cu-Mg particles, which have a noble V olta potential in air because of an altered surface film, are actively .dissolved in chloride solution after a certain induction time. Al-Cu- (Fe, Mn) particles are heterogeneous in nature and exhibit nonuniform dissolution in chloride solution as well as trenching of the matrix ar ound the particles. Light scratching of the surface by rastering with the AFM tip in contact mode in chloride solution results in accelerate d dissolution of both pure Al and alloy 2024-T3. The abrasion associat ed with contact AFM in situ resulted in the immediate dissolution of t he Al-Cu-Mg particles because of a destabilization of the surface film .