Form This specification covers an aluminum alloy in the form of extruded rods@ bars@ and profiles (shapes) produced with maximum cross sectional area of 56.1 in2 (36 193 mm2) and a maximum circumscribing circle diameter (circle size) of 20.2 inches (513 mm) (see 8.4.1). Application These extrusions have been used typically for structural aerospace applications requiring good strength and toughness combined with excellent corrosion resistance but are not limited to these applications. Certain processing procedures may cause this product to become susceptible to stress-corrosion cracking. ARP823 recommends practices to minimize such conditions.