I'd think marine grade aluminum (4000, 5000 and 6000 series aluminum) would be more desirable for corrosion resistance in salt water and being weldable than aircraft grade aluminum which is predominately 2000 and 7000 series aluminum in various tempers and not weldable.
The 6000 series, which has a much lower yield strength than 2000 and 7000 series, is commonly used on the plane's interior parts for its ductility to break forming using tighter bend radii without needing to be formed in an annealed state and then heat treated in addition to being able to be brush finished for decorative applications.
Last edited by tuco; 07-18-2011 at 09:03 AM.