Gary,

Upon looking at the failure, I am convinced that the heavy corrosion of the mast tube in the vacinity of the masthead played a key role in weakening the tube. It does so in three ways. The first way is obvious: corrosion erodes some of the metal away leaving it thinner and therefore weaker. The second way is that the corrosion always eats a very jagged, irregular path through the metal. This acts the same as a deep scratch or hole causing stress concentration. The third way is that it causes chemical/molecular changes to the metal making it weaker and brittle.

It might be a good idea on these painted masts to remove the masthead and fabricate a barrier gasket out of something and re-install. This would stop the galvanic action for good. A piece of mica is a good candidate.

I am not a fan of painted aluminum parts on boats. Anodizing holds up much better and stops galvanic corrosion much more effectively than the typical conversion coating used to prepare the mast for paint or powdercoat.

You really must not tolerate corrosion on the aluminum parts of your boat. If you start to see any corrosion, it must be dealt with by dressing out and applying conversion coating and re-painting. I'm a bit worried about the mast and beams on my old P19 and it's maybe about 1/100 as advanced as the corrosion I see in the pics.

Jimbo