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Repairing a rust hole in a car

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Step 2: Building up (part 1)

Picture of building up (part 1)
car05.JPG
At this point, I used a metal mesh body patch (bondo brand) to fill the hole, replace the missing metal, and give the bondo a place to adhere to.

Using regular scissors, I cut the mesh to approximately the right shape, and then began fitting it into the hole between the metal and the foam. Along the bottom, I had to loosen the foam from the metal a bit using a screwdriver. Since the area is curved, I had to shape the patch as I worked, and getting the last (upper left) corner in took some work.

The body patch is self adhesive, and has a removable backing. You can see in the photo where it crinkled up while I was maneuvering the patch into place. According to the instructions, I should have taken the patch back out, peeled off the backing, and then re-inserted it. But once I got it in and shaped, it wasn't coming back out, and I decided that I don't care if there's a plasticy sticker bit in there.
 
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dderolph10 months ago
Well, I admire your courage to delve into this project. However, your use of the mesh backing was not the way it should have been used. The mesh is sticky on one side, the side with the paper backing. The reason for that is that the mesh is normally applied on the outside of the area being repaired, not manipulated to the inside in the manner you did. So, you would sand and remove all rust, sanding 1/2 to 1 inch beyond the edge of the hole. Then, you would cut a piece of backing to cover the hole, remove the paper backing from it, and press it onto the clean, bare metal around the hole. The sticking side of the mesh holds it in place so that you can then mix your filler and not have to hold the backing in place while applying filler. When using mesh backing and filler in this manner, spreading some filler on some wax paper and then laying the wax paper over the backing, especially for all the area of the hole, is a good way to control the thickness of the filler you apply. If you simply spread filler over the mesh with a blade-type applicator, you may press an excessive amount of filler right through the holes in the mesh.
Brittond141 year ago
Very pleased with your post. totszwai seems to be a negative personality type. I think you did a fine job that will last well past your cars remaining years.
olmon1 year ago
Nice looking repair for your first attempt & you did follow the instructions quite well. The repair should last an acceptable length of time. (Don't pay any attention to Totszwai, he apparently doesn't know how to follow directions.) As a 40+year body-man, I would have done it differently, but I have all the equipment immediately available in my garage as well as the experience to use other materials..
jlambert1 year ago
totszwai, I have used rust preventer then bondo over it and 20 years later no one but me can tell where the repair is. It's a chemical reaction and the rust no longer oxidizes if done right.
taping off the area and cleaning off the loose rust is a good first step. But you are not ready for Bondo because the rust penetrates deeper than what the eye can see. At this point I would either and blast (or walnut shells or similar) the area or, failing that, spray the area with OSPHO. It penetrates into any "pores" After that has dried for 24 hours or so, clean again. Then spray the area with a good quality primer - two or three light coats - and let dry 24 hours before applying the Bondo!

The Bondo'd area is then sanded smooth with increasing grade paper starting with 80 and going to 120. Then, you can remove the tape and apply several coats of a "sandable" Primer.

When this has dried thoroughly, sand the area to blend / feather the repaired area to the existing painted area starting with 120 grit and finishing with a 220 or higher paper.

At this point, you should be able to wipe the area with a clean cloth, then a tack cloth in preparation for the color coats. When they have dried (you may want to sand with a 600 between coats, a final wet sanding of the area is required before applying the top or sealer clear coat.

If you take care with each step, the repair should last long after you sell the vehicle.

Note, however, of the rust was "through," that is rusted on each side of the sheet metal and you can't access the "back side," the quick and dirty Bondo approach is likely as good as one could do.
totszwai1 year ago
Wait... You "repair" a rusted hole by covering it up? You need to either grind out all the rust to bare metal or cut it off completely... This won't fix it, within a year it will come right back out, worst, it will just pop your bondo and cracks it...
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