The Al-Cu-Mg particles inherent to 2xxx
series alloys have been identified as anodic to
the matrix (Ref 6). In this case the initial dissolution
occurs in the particle, as opposed to the surrounding
matrix. The net effect is similar, in that
a pit is initiated at the location of galvanic attack.
More discussion of the impact of these copperbearing
particles on corrosion performance is
included in the section on 2xxx alloys.
While the mechanistic specifics can vary by
particle type, the result is similar. The particle/
matrix interface is a site of preferential dissolution,
resulting in the initiation of a pitting site.