What is the procedure to fix vehicle roof paint inexpensively?

Question

On a flat-roofed vehicle, what is the least expensive way to fix the roof when the clear coat has largely peeled off and rust has formed? There are no places where the rust is so extreme that holes have formed.

The owner is not very concerned with aesthetics.

I was thinking the best procedure would be to:

1. Sand the roof lightly with 200 grit sandpaper to remove some of the rust and to prepare the roof for Step 2.
2. Apply a product like Rhino Liner, Herculiner, or Rust-Oleum truck bed liner to the roof.

I proposed the plan to four people. Here are their responses:

• Persons 1 and 2: "That's a great idea. It will work great"
• Person 2: "You will have to sand the roof down to the raw metal otherwise the rust will continue to grow under the coating."
• Person 3: "I did that and the liner material started to slide off the edge of the vehicle."

What do you recommend doing to resolve this issue. The goal is to prevent holes from developing on the roof. Color is unimportant to the owner.

Answer 1

If you're not concerned with aesthetics, sand it as much as you can (the more the better), I would use 220 and then 600 because you're going to want some smoothness.

Then use one-step primer, this stuff can actually be sprayed directly onto rust and reacts with it chemically. It's better to sand the rust off but you don't have to get it all off. You do need to expose all the rust, so I would make sure to remove all the paint when sanding. It comes out black once it's done so you're going to have black, they don't have other colors as black is a byproduct of the reaction.

You've then gotta paint the primer with either BC/CC or a single-stage automotive grade paint. I think the instructions on the primer say you can leave it without painting but I would paint it since you're not going to want to be doing this again. If your not worried about aesthetics just paint the black, if you want the color right, prime the black with a regular grey our white primer and then paint that.

I wouldn't use a bedliner like Line-X. It's the wrong product for the job and you'll have problems.

So, person one is sort of right.

Person 2 is correct if you're not using the materials I mention above.

Person 3 is right if you're using something like a bedliner or have absolutely no idea what you're doing with paint.

This can all be done in a home garage with aerosol cans in about a full day, it won't look pretty but you can get the product if you're thorough.

Places you can fail:

1) You don't sand of all the paint and there's rust underneath the paint that the primer doesn't get to that then continues to grow.

2) You paint the primer before it's totally done reacting and you get bubbling and reactions that result in the paint not laying down right. Check the can for instructions on how long you should wait)

3) You don't wipe down the surface before priming with a grease and wax remover, mineral spirits, etc.

DISCLAIMER: THIS WILL NOT LOOK PRETTY, IF YOU WANT A PERFECT JOB, GO TO A BODY SHOP AND GET THEM TO PAINT THE ROOF, THEY'LL PROBABLY CHARGE YOU 100-200 BUCKS.

Answer 2

Person 2 is right on the money. Sand it down to bare metal, get all the rust off. As for how to cover it, if you prepare the surface adequately (sand it smooth) and use a primer, whatever you apply on it should stick. Many people apply some kind of sealant (often epoxy-based) to the bare metal before priming it.