This example of a pitted surface was produced by exposing a specimen of aluminum A92519 to 3.5% NaCl during seven days. The width of the picture is approximately 1 mm.
The corrosion attack of aluminum of the 2000 family is mixed. While most of the surface is uniformly pitted (yellow arrow), as A92024 would do in similar conditions, we can see the formation of deeper pits (red arrow) that are surrounded by unattacked regions (blue arrow).