FWIW, I manufacture crop dusters, Thrush Aircraft to be precise. Corrosion
protection is more important on a crop duster than any other aircraft except maybe for a float plane kept in salt water
. The airframe is 4130 chrome moly tube steel
and has been for the last five years or so powder coated as powdercoating gives vastly superior corrosion
protection than wet paint
on steel parts
. Powdercoat can be touched up with wet paint
Anodizing is a very good corrosion protection for aluminum but is rarely seen on aircraft due to it changing the physical properties of aluminum. Usually aluminum is alodined, we alodine every aluminum part on a Thrush and then paint it.
The material is very important in choosing which method for corrosion protection, you can't anodize or alodine steel of course, steel you cad plate. I've had very good luck with powder coating steel, maybe not so much for aluminum though.