Abstract
Real-time in situ optical microscopy observations of the initiation behavior of intergranular corrosion on artificially aged Al-4.5Cu and Al-4.5Cu-1.5Mg were performed in naturally aerated 0.1 M NaCl at pH 6.0. For both alloys, the discoloration of intermetallic particles occurred before intergranular corrosion, and a discolored coarse intermetallic particle on the grain boundary acted as the initiation site for intergranular corrosion (Al
2
Cu for Al-4.5Cu and Al
2
CuMg for Al-4.5Cu-1.5Mg). The discoloration of Al
2
Cu particles was localized and occurred only on a small number of particles. However, almost all Al
2
CuMg particles were discolored; the overall surface of the particles was discolored uniformly. The discoloration of Al
2
Cu on Al-4.5Cu led to micropitting. In contrast, the discoloration of Al
2
CuMg on Al-4.5Cu-1.5Mg caused the trenching of particles. The difference in the initiation behavior of intergranular corrosion was discussed in terms of these precursory phenomena.
Funder
Japan Society for the Promotion of Science
Light Metal Educational Foundation
Publisher
The Electrochemical Society
Subject
Materials Chemistry,Electrochemistry,Surfaces, Coatings and Films,Condensed Matter Physics,Renewable Energy, Sustainability and the Environment,Electronic, Optical and Magnetic Materials