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Discussion Starter #1
My '99 Outback has some rust on the rear panel. I spent a good hour and a half using a grinder attachment (on a Dremel) to blow away all the surface rust, rip through any spots rusted through, and get down to the bare metal. The reality is that there is probably still some rust that I just didn't get. In fact, between the panels there is a bit of surface rust I cannot get to but I have tried to just punch out the metal curves in on the top panel. This way any rust on that is just gone and drops to the ground.

I was wondering if I could do the following:

1. Use rustoleum auto primer as a rust inhibitor on the entire surface area that I have sanded down to the bare metal. Here I'm trying to get the rust inhibitor on the metal to slow down the rust spread. Would a Loctite or this "POR-15" maybe work better?
2. Use bondo to patch up the holes.
3. Use a regular primer (likely an epoxy)
4. Spray a Duplicolor Perfect match auto paint - acrylic lacquer
5. Spray a Duplicolor protective clear coat finish

Are there major holes in this plan? My goal isn't to get a show room finish.. I would just really like this car to last for 5 more years on the body - I live in Wisconsin so that's tough.

Let's just assume I'm not cutting out the area and welding in a new piece. Any input is really appreciated, thanks.
 

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Bottom line - If there is any rust you cannot get out the repair will not hold and will fail. It may take some time and may look good for a while.

That is why it costs so much to restore a vintage car. These guys cut out the rusted areas and replace with new panels. Or, even remove the entire panel and replace with a restoration panel. It is not cheap to do it correctly.

But, if you can live with it; go for it.
 

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If you aren't going to weld in new metal, consider skipping the bondo layer so it's easier to detect new rot later.

Plastic fillers like bondo can trap moisture and hold it close to the metal, which accelerates future rot and hides it from view, often until it is extremely advanced.

In other words it works great for hiding corrosion damage, but it is counterproductive if you are actually trying to keep the car nice. How long do you plan to own it?
 

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I own 4 Subarus. A 95,97,02 and a 14. The first two are 2.2 and the last two 2.5.
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You have to cut out the rusted panels or the rust will come back pretty fast. Change your drumel to a cutting wheel. If you have a 1/2" perforation, cut out a 3" hole. Then use the converter, fiberglass, bondo, primer and finish coats. It will last 3+ years depending if you get all the rust.

I don't think that the converter does much but I still use it.
 

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Discussion Starter #5
If you aren't going to weld in new metal, consider skipping the bondo layer so it's easier to detect new rot later.

Plastic fillers like bondo can trap moisture and hold it close to the metal, which accelerates future rot and hides it from view, often until it is extremely advanced.

In other words it works great for hiding corrosion damage, but it is counterproductive if you are actually trying to keep the car nice. How long do you plan to own it?
I'm hoping to get 5+ years (only 3 would be fine I guess) out of the car.. luckily it's white so just about any pure white paint job will blend in decently. The holes are already there from me punching out the rust so it would look pretty lousy without filling in the gaps. Maybe I'll post in a picture tomorrow of where I'm at. Just bought it and didn't give it a thorough look on the rust, my mistake for being lazy.
 

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Discussion Starter #6
mikec, I'm pretty sure I've dug out all the areas that are rusted through.. by perforation do you mean a mesh overlay to spread the bondo on?
 

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I've had rust battles on a Honda CRX I used to own. I tried the rust converter stuff once, didn't have good luck with it, rust reappeared not long after.

What I did have much better luck with and continued to use up until today is Permatex Rust Dissolver Gel. This stuff is also known as "naval jelly" (naval, as in the US Navy). This stuff turns the small surface rust black. Apply it, wait 10 minutes, rinse with water, then repeat several times. I make sure any rust removal/restoration job I do has this step included, even if it seems like I've managed to remove all rust via standard physical methods.
 

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I own 4 Subarus. A 95,97,02 and a 14. The first two are 2.2 and the last two 2.5.
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kidge

By perforation, I mean an area that you punched through with your grinder. There's rust on the inside around the perforation that you can't see. Thats why you have to cut a hole much bigger then the perforation. The fiberglass is needed to bridge the hole.

If it's just surface rust that does not extend through the metal, I've had good luck by grinding, using naval jelly to highlight where there is still bits of rust, grinding again with the drumel pencil grinder, and then bondo [to smooth out metal], primer, and finish coats.
 

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Cut, remove, replace. If even a pinhead of rust is left it will grow underneath any repair you do. If there is rust inside or in an area you cant get too, it will grow. I tried grinding, sanding and Naval Jelly along with primer and paint, in 2yrs the rust came back even stronger than originally.

Now, you can fake it, I had a rear hatch on a Durango that had rust along the bottom. The rust was quite bad IMO (rusted through in a couple small spots). I sanded, ground and used fiberglass to cover the area, then I sanded that and painted it. The rust will still grow underneath, but the fiberglass will keep it solid and looking better than bubbled up rust under paint and will keep you good for a number of years. I used two layers of fiberglass, 3 would be better though.
 

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Discussion Starter #10


Surface rust overnight.. I might even consider using Bondo to build of the wheel well but that's probably rusted up too. Also can I prime and seal the area before applying Bondo? I want to seal off the metal part of the panel best I can form the elements. Just worried the Bondo might not adhere correctly over layers of primer and sealer.
 

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Don't fill it with bondo, it will just trap water and cause more rust. I'd recomend cutting it out with a grinder, sealing the inside with por15 or something similar, fiberglassing it if you don't weld, use some surface filler on it to smooth it out and paint, that will last longer.
 

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Thats gonna rot no matter what you do. Thats actually pretty extensive, there is likely rust all over inside. I have a similar situation (not as bad) that I am going to attempt to fix.

I will be spraying the heck out of the inside with some aerosol rust blocking primer (though i know it wont work but hope it slows the progression), then going to spray in some 'Great Stuff' foam, sand, fiberglass and skim coat it with bondo, and finally paint to match with some color match paint.

Not much else can be done unless you cut and replace a large portion, and the cost is not worth it.
 

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Surface rust overnight.. I might even consider using Bondo to build of the wheel well but that's probably rusted up too. Also can I prime and seal the area before applying Bondo? I want to seal off the metal part of the panel best I can form the elements. Just worried the Bondo might not adhere correctly over layers of primer and sealer.
bondo sticks to primer...
 

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13 blk Outback 2.5i cvt AW package, bunch of other OEM accessories...12 blk F350 6.2 gasser 4x4...10 Goldwing red nav ...04 JD 4510 loader/bhoe
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In the OLD days we used lead as the filler. Lasts forever and does not fail. But, being lead you know the deal now. Don't use it.
It did not fail as its very soft and flexible.

If you have a void, back it with a fiberglass screen, if small. Larger areas just cutout and replace the metal. Skim bondo either as needed. Most failures are not due to incompatibility but, just using to much bondo. The weight of it over time vibrates it loose from whatever its attached to. Also, metal work is much more flexible than any bondo which is very rigid once it fully sets.

Good luck and apply thin!
 

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I use a product called Duraglass which is cut up glass fibers on non-water absorbent matrix. So I cut out the rusted areas, fabricate sheet metal patches and weld them in, then a coat of Duraglass and then a thin finish coat of bondo. If possible I also try and spray rust preventative primer and paint on to the inside of the repaired area. I've had lost lasting repairs using this procedure.
 

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Discussion Starter #18
Repair holding up .. winter will be the test

With a lot of work searching for rust.. hours and hours - I came to a finishing point and put a bondo layer outside and inside. Cut out and ground away a lot of rust on the inside frame and used a rustoleum converter to prime it. On the outside, I used a rustoleum primer, then painted with a top coat applied (2 or 3 applications each). The winter months will be the test..

My advice to anybody is to keep grinding away until you're a good inch past any rust you find just to be safe. And if you think it's just surface rust, think again. Hit the surface to check the integrity of the steel. If it seems weak, it is. Why? Rust. Cut it out. In general, odds are the rust is far more extensive than you imagined. :29:
 

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True enough... Think of the iceberg analogy. Here are a few photos of a recent rust repair I did on mine. The thin cardboard pattern really helps in getting the piece cut to shape.
 

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^ What would that cost to have a shop do it? I am interested in removing the rust on my rear quarters but do not have to skills or equipment for that level or work.
 
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