Rust Patch Repair

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I have a small 8"x3" area under my rear door that rust is taking over the paint. it is kind of bubbly. I would like to repair this. What would be the best route? I have some rust remover. Should I apply that, let it do it's thing, clean it up, then maybe sand the area with steel wool and use touch up paint? I have some rubbing compound and some polish as well. should i apply those after the touch up paint? or maybe just the polish? or is there a better method? i'm a detailing noob.
 
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I understand what you're facing; it's not a bad idea, but you're kicking the can down the road. I did it on my Mustang last spring; dug out as much as I could, coated it with remover, sanded, sanded, sanded, coated with Master Series Silver, some bondo, more primer than paint. It's way better, and I'd probably do it again. But I can just see the beginning of a new spot forming. At a minimum, you gotta get it from the inside. Kevin
 
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It's coming through from the inside out. The paint is all that's holding it together. Pictures? Sounds like typical rocker panel rust. Poke the bubbles with a pencil. Metal will not poke through. You want to cut it out, a $10 HF angle grinder with 1/8 cutoff wheel will do fine. You'll cut a much bigger hole than you expect to get back to good metal. Spray the insides of the now accessible panel with your favorite rust converter, then top that off with your favorite (oily) top coat. Use cardboard to mock up how you'll bend up some "tin" with vise grips or a metal brake if you can find one. An old computer case is a good metal donor. Cut about an inch oversize. Bend little "over/under" flanges to fit your existing panels. Attach with self-tapping screws then back said screws out and replace with Pop_Rivits. Cover with bondo, sand, paint.
 
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Under the rear door? Through the rocker panel? This isn't good news. Can you remove the scuff plate and get access to the inside or are there plugs on the backside that allow access? You can do a cosmetic repair to the outside using a rust remover, a rusty metal primer and then finish paint, and in this area, the paint imperfections you're bound to have won't be too glaringly obvious. You will find holes once you grind of the bubbles, so you'll need at least a little epoxy filler. To keep the rust from coming back after the first rain, though, you need to treat the inside surfaces where the rust started. If you can gain access to do this, your repair should last for a few years. A more permanent repair would involve cutting back to clean metal and then welding a patch panel in. Not sure that you'd want to do that. Now, if it's really just the bottom of the door, interior access is easy and it'll also be easy to clean out the clogged drain holes that you'll probably find that caused the rust through in the first place. It would likely be easier to fix the existing door than to hang a yard one and get it to fit and close properly.
 

BrandonVA

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hopefully it's not as bad as it sounds. i'll snap a pic tomorrow. dang salty roads! everything else on this car is pristine! i've heard some people drilling small holes under the rusty rocker panel areas. would this be a good idea to mitigate future damage? I could also spray rust inhibitor into a hole.
 
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You could drill about a 3/4" hole and stick a dentist mirror up in there to look around, and putting in some sort of aerosol rust preventative. They sell plugs for capping off after doing just this.
 
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The restoration guys cut the rusted section out, make a patch, and use a plasma rig to weld it in place with a series of small welds which don't distort the surrounding area. Then they grind the whole thing flush. I've seen them REMOVE a sunroof from a classic car and weld up the hole. With proper sanding, blocking, and paint you would not know it had ever had one. In your case it's cheaper to get another door.
 

BrandonVA

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hm, ok . let me check it out again today. when you talk about drilling a hole. do you drill from the top (inside the car) or from the bottom (outside)?
 
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your choice. Going thru the bottom would let you see how thick the metal is though.
 

BrandonVA

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just checked today and there are holes about every 10 inches are so from the factory with plugs in them. I'm thinking I could spray some sort of rust inhibitor through these holes to prevent more corrosion from occuring. Is there a good product for this? There are also holes on the top side already under the removeable trim piece. I will probably spray some in there as well.
 
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There you go! PS, those holes could still be distributor/ importer/ dealer drilled. I'd be curious to see a parts image of your rocker, with holes in same spot.
 
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Originally Posted By: BrandonVA
just checked today and there are holes about every 10 inches are so from the factory with plugs in them. I'm thinking I could spray some sort of rust inhibitor through these holes to prevent more corrosion from occuring. Is there a good product for this? There are also holes on the top side already under the removeable trim piece. I will probably spray some in there as well.
Good. For your sake, I was hoping you'd find such holes, since they're commonly there. Treat the inside completely, since that's where the rust is coming from. You might want to do the cosmetic repairs to the outside first, since whatever you apply to the inside may not play nicely with either rattle-can paint or body filler and will likely drip out of the newly revealed rust pinholes for a time. If you can find a rusty metal latex primer for the outside, that would be good since it'll be totally impervious to the solvents in whatever color coast you use. DuPont used to offer a really effective latex rusty metal primer that I've had good results with, but I haven't seen it available lately. DO NOT use steel wool as a prep abrasive. I don't think that you want to introduce rusty metal dust into your repair, which is what you'll get with steel wool.
 
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