Rusted hole - body filler - what if I can't get all the rust out?


Old 10-14-18, 06:25 PM
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Rusted hole - body filler - what if I can't get all the rust out?

My understanding is that absolutely all rust has to be removed prior to applying body filler and paint.
In this case there a hole and it's going to be hard to get up in there even to view much less scrape out any rust up there.
If I'm unable to get all the rust out and stuff in the body filler and paint over it, is the leftover rust going to spread from underneath rendering the repair job useless?
I see this area rusted on a lot of trucks so surely there must be a way to properly deal with this.
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Old 10-14-18, 06:35 PM
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Use rust converter before you apply any body putty.
Old 10-14-18, 08:28 PM
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ok so spray rustoleum "rust reformer" all up in there and then bondo it up and spray?
Old 10-15-18, 01:59 AM
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The rust converter is sort of a band aid and doesn't remove the rust it just chemically converts what it touches.

Ideally you want to sand, grind, or sandblast rust away before doing body work, then finish. You also want to seal the area to keep water out so new rust doesn't form,

That looks like a wheel opening so bet it's open on the back side which is where the work would take place,
Old 10-15-18, 04:02 AM
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Filling a rust hole with bondo is more of a temporary fix. To make a permanent fix you'd need to cut out the bad metal and replace with new. Unless I was willing to go that route I'd just clean it up the best I could, use a rust convertor, bondo, sand, primer and paint. It will probably last long enough unless you plan to keep the car for a long time.
Old 10-15-18, 05:22 AM
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I agree that whatever you do with that hole will be temporary.
The proper way to fix is to use a fender repair panel which should be available for your vehicle.
A repair will last longer if you use chopped fiberglass filler rather than lightweight auto body filler to fill the hole.
Also, a fiberglass patch over the hole and feathered into the surrounding surface will last even longer.
Old 10-15-18, 06:08 AM
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A back side of a rusted hole in the fender well is almost impossible to reach from the backside. Therefore, the rusting will continue even with the best patch so the fix will always be temporary. Even a welded path will rust unless there is some way of undercoating the backside after welding because water will get in. Good luck.
Old 11-02-18, 07:57 PM
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I agree that the best repair is to remove and replace the entire rusted panel. I have used rustoleum rust reformer (it’s a rust converter) but only where I could remove the loose surface rust first and applied a second coat or top coat of another paint.
I own two collector cars that were restored 24 and 20 years ago. Some of the enclosed channels began to develop surface rust. More than a few years ago I applied Rust Encapsulator from Eastwood (it’s not a rust converter). Spray cans come with 24 inch flex tube with nozzle that sprays sideways in all directions. Ran the tubes down frame rails and body inner channels that aren’t visible - has held up very well. Check it out.
Old 01-21-19, 07:50 PM
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Not a proper fix, but this is what I did.

Spray Fluid Film (lanolin oil) through and around the hole and any hole that you can get behind fender.
Fluid film does not fix rust, but it will slow down additional rust from forming by blocking water out.

Then, install fender flares. You can paint fender flare to match your vehicle's color if desired.

If you really want to fill the hole with body filler, grind out as surface rust until you see bare metal. Spray fluid film in the hole toward fender as best as you can. Then you have to clean fluid film off the surface before you put body filler.

If you managed to cover all rust with fluid film, it will slow additional rusts from forming.

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