Looking at my image posted here you'll notice paint deterioration on our porch rail.
This was replaced about 20 years ago with treated 2 x 8s.
The wood has not deteriorated and is holding up well.
I painted it about 4 years ago with a good primer, along with outside enamel paint.
The moisture is (must be) coming up from under the painted surfaces and blistering the surface.
This railing is protected from the weather, although it will receive some rain, snow, melting, and sun.
I'd much prefer to cover the rail rather than paint it, if I cover it it must not be done with anything that's not top grade, meaning no chance of wrinkling, buckling, or other ways of being damaged.
I've just been made aware of my Sherwin Williams rep. there is a primer that is thick and will cover nicely , then need to paint over it with the final coat.
What do you think?