I built a Bounty about 30 years ago and after about 20 years corrosion began to show up on the metal of the cannon balls I had picked up at the local hobby store.Being quite new to the game at the time I am sure that I probably didn't take any steps to seal them in any way.I have heard of this happening to even some ship models in museums.What is it and how can it be prevented.Is Britannia metal subject to the same problem?
Thanks guys!

Ahoy John!

Corrosion, can be avoided on any porous metals by sealing in some manner...the cannon balls that you originally bought were more than likely a steel cast product, which of course, will begin to rust if not protected...a clear, matte sealant should work for sealing the pores of the steel and prevent any corrosion...did you paint the cannon balls with an enamel, or were they self colored? This should have done the trick, if moisture and humidity isn't a problem in your area...as far as brittania metal, corrosion per se shouldn't be a problem, as true brittannia is made up of mostly tin...maybe a discoloration with time, but not a corrosion, mate...hope this helps some!
~Gunny