Learn me: Halting sheet metal surface rust and long term protection

A recently acquired project has plenty of surface corrosion (AZ sunburn) on the sheet metal.  It's going to be a long time (years) before it's ready for bodywork and paint, but I feel I should do something to stop any further degradation.  I've never been in this situation before, but I want to be sure whatever I do doesn't make it significantly more difficult to prep for paint in the future.  I do plan on media blasting the car when that time comes.  Not planning on any bodywork right now, just want to preserve and protect the sheet metal until the time comes.

Most of my searching has resulted in lots of info on how to preserve patina (Rat Rods, etc), or chassis work and hard to reach places, not body panels that will eventually be painted and expected to look nice.

Current condition:

With some quick sanding with a scuff pad:

It's obvious there's still corrosion present, so I'm thinking some kind of rust converter would be necessary.   What I haven't been able to determine is if things like POR 15 and Eastwood Rust Coverter will play well when it comes time to paint a few years down the road.  Most of them require a top coat, so would a sealer primer/ epoxy primer work for that?  Just assume I'll be taking back to bare metal at paint time?

The other thing is that many products say not to clean the surface, and that they need rust present to work properly... if you apply it over rust, do you just take it down to metal when eventually prepping for paint, then prime as normal?

I appreciate any input, or any product recommendations for the job at hand.  If there's a forum out there (or here) that has any good threads on the subject I'd love to read them. 

In reply to Rodan :

I have had extremely bad luck with POR15, following the directions (no loose rust, color is okay).  I peeled the paint off in sheets after a couple months.

As an experiment, I'd try a shop towel soaked in evapo-rust covered in plastic.  If you can keep the towel from drying out, it may remove a good bit of the rust.  If that works, you could hit it with a coat of self-etching primer for storage.

JoeTR6 said:

As an experiment, I'd try a shop towel soaked in evapo-rust covered in plastic.  If you can keep the towel from drying out, it may remove a good bit of the rust.  If that works, you could hit it with a coat of self-etching primer for storage.

I have to agree with JTR6. While I have never used Evapo-Rust I have heard good things about it. The roof will be pitted once your remove the rust but the etching primer and then when you're ready to paint several coats of filler primer and  sanding, you should be able to get a smooth surface.  

For all our long term project cars in the shop (sitting in bare metal for years in Houston humidity) we would wipe them down with Gibbs.  It's similiar to WD-40 but leaves a film on the metal.

Lots of people swear by Gibbs, it's also not supposed to cause any problems when you get around to paint in the future.

I would treat it with Evaporust or similar first.

Recently played with this. Find it a bit more useful than evaporust, though not as effective as long term immersion in evaporust (obviously)

https://www.lowes.com/pd/Rust-Oleum-32-OZ-Spray-Gel-Rust-Dissolver/1002035750

I'd do some power tool driven removal of scale (something like angle grinder scotch Brite?) Then spray this, wash and paint with something effective and cheap.

I've used Ospho in the past to prep metal before priming and painting or protecting bare metal. It's mainly phosphoric acid (same as Coke!) and converts surface rust like that to iron phosphate which is black. It's about the consistency of water and a bit sticky when dry, I've used a cheap foam brush to apply it. Clean up before primer and paint will be easy but depending on how long the car is left you may need to reapply if you notice surface rust starting to form but that won't take long to do.

Something like POR-15 isn't going to fun for an application like that, it's more of a finish you would use for the underside of the car and I think you would end up removing it before doing body work down the road. That might be easy like Pete's experience (which is not how it should be) or really difficult if things go the way they should. I feel like anything oily will also be troublesome to clean up down the road as well before paint.

Thanks for the suggestions guys.  I would prefer getting some kind of primer on it, since it will by necessity be stored outside, so something like the Gibbs probably won't work.  I'll do a test with the Evapo-Rusto or the Rustoleum product linked.

Has anyone used Rustoleum Sealer Primer with good results?