Cast Iron and the preservation of.

[Okeanos]

That has to be worth quite a lot!

As to preserving submerged cast iron, I found this:

http://www.ndt.net/article/art2008/p...093Bartuli.pdf

The problem with the cannon is the state it's in and unless provenance can be shown it's not worth a lot.

The above article is interesting but is for in water preservation, you'll still have the same problems if removed from the salt water environment.