[TowerTalk] Aluminum longevity?

[KT2Q]

All:

Before I go to the trouble of coating the exterior of my new M2 Yagi, is 
aluminum corrosion a real problem with the alloys used today?

Shouldn't the natural oxydation protect the surface of the antenna and stop 
corrosion? What about the inside of the elements and boom? If surface 
corrosion is a real problem, what's the sense of protecting the outside if 
the inside is left bare?

I have a F12 antenna that's been up for 6 years. The aluminum is certainly 
dull, but I don't see any corrosion. The clamps are rusted to hell, but the 
rest is in fine shape.

So, what's the average life expectancy of aluminum before corrosion takes 
it's toll and the antenna needs replacing?

73, Tony KT2Q