Primer question

[mocwon]

4X4Poet is right on the mark. Regular primers may seem to be okay but down the road you run the risk of the paint peeling or rust developing under the paint.

Originally Posted by 4x4Poet

Most plain and guidecoat primers are porous. They allow water to microscopically seep thru to the metal and cause rust underneath the coating. If the truck is always inside, doesn't matter. If outside, then only a primer-sealer will prevent water from penetrating the primer(-sealer) coating to the metal. You can leave a primer-sealer on outside as long as it stays bonded to the metal. For your welding work that will ruin small patches of previously sprayed primer-sealer, have the paint shop mix up some primer-sealer in an aerosol can so you can reapply to just the parts you've welded around.

Verify this with your local auto body paint supplier. The staff will likely know this info from experience, whether personal or with customers. Besides, they will give you the best recommendation regarding waterproof primers.