If the crud were chiseled off, they might look a little better
On iron pieces recovered from saltwater like these, old ones, the chlorides from the salt water leach in from the outside-in and from the bore-out at the same time, so most say 18th C. guns are pretty well full of chlorides. They cause the iron to flake apart. Taking flaky iron off the outside just exposes flaky iron deeper down, so I don't think you will find guns like this that get better-looking with removal of outer layers.
One exception I've noted is the very heavy Civil War-era siege and seacoast guns that came from a sunken barge off the US southeastern coast. The iron on those is so thick that in 100 years the chlorides didn't penetrate all the iron, and some folks have been able to grind down the worse spots to restore them to the same general shape they had orginally, with lots of body putty etc. required to fill in the larger potholes. However unless someone has spent the time and money to put them through an electrolysis treatment, they won't be stable and will need rework over time as more metal flakes off,
