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Painting from the rust up

Discussion in 'Early Jeep Restoration and Research' started by JZ, Aug 14, 2005.

  1. Aug 14, 2005
    JZ

    JZ Member

    Huntsville...
    Joined:
    Jul 27, 2004
    Messages:
    140
    I've finally gotten serious about putting a finish on the tub and I gotta ask about the process. There is a shinny new piece of passenger side floorboard and support frame. And, there is the old, old paint on the outside, rust on the inside, toolbox. I am on my sixth or seventh wire brush in taking down the old paint (mostly to find the rust underneath).

    My question is: How many of and in what sequence do I apply the following products: (a) Ospho (or similar), (b) rust-encapsulator/hammerite, (c) bed-liner, (d) bondo, (e) etching priner, (f) filling primer, (g) finish paint?

    On the shiny metal?

    On the rusty metal?

    Over old paint?

    The various descriptions that I have seen on the web have left me confuzed.

    [​IMG]
     
  2. Aug 14, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    Ok, I'll give it a try. Not a lot of experience, but I've done some research. Seems that everybody has their own combination, so there's no really specific answer.

    Let's see if we can divide it into categories by substrate: bare metal, old paint, surface rust, and deep rust.

    For bare metal, you'd use etching primer or epoxy primer. On top of that, you'd use filler primer and color coat.

    On old paint, you can skip the first primer coat if the paint is in good condition and not too thick. Thick paint can be stable, but it's not very scratch/chip resistant. For bondo, you want to have a surface with "tooth" (ie 40 grit prepped) so smooth paint is out. You can leave some paint under bondo though, if it's solid and roughened.

    Surface rust is probably good for Ospho or similar. I had thought that Ospho or Picklex was intended to stabilize bare or rusty metal. Whether you can put epoxy or filler primer on top of that would depend on what the manufacturer specifies about what can mix with what. I'd think you could use Ospho in place of etch, and then put filler primer on top of that - but you'd better read the instructions to make sure.

    For deep rust, I think you either have to grind down to bare metal or use one of the rust-specific paints, like POR-15 or Rust Encapsulator. These can be top coated, so I'd expect you could put your filler primer (or even the color coat) right over it. Again, the manufacturer will specify what top coats are compatible.

    For bed liner, I think it's basically the same as a color coat. It can be applied over color coat too.

    Another comment re bondo - typically you'd apply the bondo over bare metal and old paint, and get your body contours where you want them. I think you'd have a tough time putting bondo over POR-15 (for example), because you need some tooth to hold the bondo, and the POR-15'd surface is both hard to scratch up and fairly rough, since it's on top of rusty metal.
     
  3. Aug 14, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    Use Ospho on rusty areas. Use etching primer on clean metal. Only apply bondo to clean metal. Use filler primer only to smooth and blend. You can top coat over etching primer, but I recommend a regular primer over the etching primer, over Ospho and over all old paint. Bondo has to be sanded smooth or nothing will stick to it. Even if you wire wheeled it, lightly sand bare metal to help adhesion. Wiping with a cleaner is recommended to remove sanding dust/oils etc. So, you've got Ospho, bondo/etching primer, regular primer over all, top coat. Of course in some areas you might want to use the Hammerite or bed liner instead of a finish paint coat.
     
  4. Aug 14, 2005
    JZ

    JZ Member

    Huntsville...
    Joined:
    Jul 27, 2004
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    140
    Thanks for the good comments/directions. I have continued to sand/wire-brush down to bare metal (slow-slow process!). Once the paint is all off, the shiny metal almost begs for just a clear-coat. There is just so little of it.

    I a couple of areas (like the floor below the gas tank), the ancient rust has left many pin-holes. These only appeared after I attacked the roofing tar and bondo layer under the tank. When I got down to just metal, there were the holes. I cannot get a finger through any of them, but the metal around them is thin. Is there a suitable adhesive for overlaying a thin (24 g?) doubler? It is worse behind the spare mount (MIA), where I will be forced to weld in a patch.

    When I started this I had no idea that I would become so picky.
     
  5. Aug 14, 2005
    Old Bill

    Old Bill Aggressively passive....

    Really Southern...
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    Nov 12, 2004
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    822

    I patched the passenger footwell and under the gas tank (both of which were full of pinholes like you describe) with pieces of 24 gauge. I used SEM's RustStop to treat the affected areas, and applied an etch primer, scuffed it really well, and applied the patch with, are you ready for this?, windshield urethane. The same stuff they use to put in windsheilds. I got this tip from a body man, who showed me a patch he did with it, and I can say this from experience, there ain't NO way water is getting in between those two pieces of metal from any angle. The urethane pushed it's way through every pinhole and around the full perimeter. It was a whole lot easier than cutting and patching.
     
  6. Aug 14, 2005
    JZ

    JZ Member

    Huntsville...
    Joined:
    Jul 27, 2004
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    140
    Great info, thanks Thad!
     
  7. Aug 15, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
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    23,596
    IIRC the windshield urethane is similar to body adhesives sold specifically for body repair. Popular today for things like roof panels, which tend to warp when welded.
    http://www.lord.com/Default.aspx?tabid=1146
    Should be available where you buy paint & body supplies. Eastwood sells a comparable product.
     
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