I have seen a few boats out this way with painted spars. We don't get the super high temps that you do, of course.
If I were in your situation, I'd pick up a phone and call a mast manufacturer (Hall spars, etc.) for advice. Whomever you call, be sure that they have experience with customers in your environment.
Hopefully you can stay with a marine product. That would be expensive enough, I'd hate to think what "aviation" on a label does to the price!
I wouldn't talk to a paint company or worse, a marine store, until you talk to someone who's actually used the product in that environment.
Hope this helps.
Mike
Imron is used quite a lot in the marine industry too. I just pointed out aviation as an example where they have aluminum structures that need to withstand some very extreme conditions.
Good to know, thanks for the clarification.
By all means, cheaper may not be better, but in any event, I stand by my recommendation to call a professional user before making a purchase.
No offense to anyone's opinion/experience here; rather, this is something you're only going to want to do once and not experiment with multiple gallons. Trying out a small sample is a great idea if you can do that.
Mike