The 2000 series alloys are made up of copper and aluminum. They are strong, corrosion resistant and can be machined and extruded easily. 2000 series finds applications in truck paneling, aircraft structural parts and building curtain walls (outer floating facade on most modern buildings). The 2000 series is ideally suited for these applications because it gains structural rigidity by precipitation hardening (age hardening).
There are a few drawbacks however. The 2000 series is difficult to anodize due to the high copper content (up to 6.8%). It can be anodized, but coating thickness is minimal in comparison to 6000 or 7000 series aluminum. Also, parts made out of the 2000 series may suffer “stress corrosion cracking” – a sudden unexpected failure of a ductile metal.