Date registered: Oct 2005
Vehicle: '72 250/8, '76 200d
Location: '79 300sd, 79280se
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Shade tree rust repair
Methods I've used:
MATERIAL:Muriatic acid(inexpensive solution of hydrocloric acid sold thru home centers,hardware stores, masonry supply)is a very strong, potentially dangerous acid that is capable of getting steel spotlessly derusted.
CAUTION: Rust removal is not a recomended usage listed on product label. DO NOT GET THIS STUFF ON ANY PART OF YOUR BODY,ESPECIALLY YOUR EYES. USE OUTDOORS. DON'T INHALE FUMES. BE CAREFUL WHERE THERE ARE PETS. DO NOT USE WHERE THERE IS ANY CHANCE OF CHILDREN MAKING CONTACT WITH THE ACID. NASTY STUFF. PLEASE BE VERY CAREFUL WITH THE ACID!
METHOD:Mechanically clean area as well as possible. Brush acid on repeatedly over a period of hours until metal is sand blasted-like clean(sand blasting is preferable method if available/applicable). Rinse off. Treated surface will get a slight coating of rust almost immediately if exposed to any moisture. Rinse really well and dry with heat gun or hair dryer. Primer immediately.
APPLICATIONS:One area I used this method on was the rust-prone area on either side of the trunk of w114 and w115 cars where there is a crevice about 21/2-3 inches deep that is usually rusted due to water leaks into the trunk(around tail light lenses, from rear window via rear window deck, maybe some from rubber trunk seal).
RUST REMOVAL: There really is no mechanical way to get to this rust. The proper repair is to cut out the rusty metal and replace the body panel with a new one. I could not afford to have this done on my cars. So-I cleaned out the area with acid as well as I could and then primered the metal remaining by spraying lots of primer into the area.
EPOXY: Then I closed off the the(rust) holes to the outside with duct tape and blobs of bondo. I then mixed up epoxy glue(Tap Plastics, Marine supply, Builders Suply, Home depot etc.) and pored it into the crevice till it was level with the top (now no water can collect here). Make epoxy more viscous, so that it won't run off or sag, with wood flour(very fine sanding dust)or commercially available thickeners(Tap Plastics,marine supply outlets)
FINISHING: I cleaned off tape and bondo from the outside and sanded the repair flush with the body. I finished off the repair with bondo and paint.
OTHER APPLICATIONS/MATERIALS:I also restored the trunk floor and interior foot wells of this car(puddles of water that I traced back to the rear window-via the bulkhead behind the rear seat) the same way, using fibreglass cloth to bridge the holes in the badly rusted sheet metal. I decided on this occassion to finish over the repair with liquid truck bed coating to make an attractive and durable surface.
CONSIDERATIONS: You would not want to use these methods if you were restoring a really valuable car, unless you were just wanting to preserve the car and make it usable until you could get around to, or afford, professional bodywork.