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Rusted Frame Repair

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dcr:
Anyone have experience with rust repair on a frame? There are a few spots where the frame has rusted through, but not to the point where structural integrity is in question. I am think i can cut the spots out and weld in a piece of plate. Anyone have a thought on this?

Bikenstein:
Dcr, it would depend on where your frame is rusted as to whether you would change the integrity. Pictures would help. It is possible to cut out patch and grind an area to look original without causing a problem. A couple of things to keep in mind are the material used and also the welding methods. Use a mild steel plate or tubing section equal to or slightly greater than the frame thickness. Make sure the frame and metal used is clean of paint, rust, or grease well past the weld area. Use a mild steel rod. E-7018 will be best because of the nickel content. Use 70 s wire if tig welding or 70 series mig wire. T.I.G. welding would be best because it would allow you to use the least amount of heat and still get 100% penetration. The more heat you apply, such as when stick welding, the more the chance of overheating the metal. When you do that there will be an excess of carbon drawn into the weld and this can make it brittle (hence the nickel in the 70 series rods). The crystal structure of the metal will be permanently altered making it prone to cracking. Also avoid square corners if the patch is in the tubing. Radius the holes or do a diamond like cut so there will be diagonal lines instead of cutting 90 degrees to the frame. If the area to be repaired is in a reinforcing plate it won't be as critical. I wouldn't recommend brazing or oxy-acetylene welding on a frame. If you are an experienced welder, fine, but any heat applied to a frame is a critical operation as you can easily cause weak spots even if you scab plate it.

dcr:
Thanks for all of this great information. I haven't gotten the frame blasted yet so pictures probably wont do much at this point. There are a couple of rust spots that are a little more than just surface rust, but they are on flat areas of the frame. I am hoping that once i get it cleaned up, it will be a simple fix, as simple fixes like these go. I hate to scrap this frame and have to go looking for a donor bike, but that might end up being the case.

Once i get the frame stripped, i will post some pictures of the trouble spots. Thanks again for your help.

dcr:
Here is a photo of the only area where the frame is rusted through.

Bikenstein:
Don't see any problem with repairihg that. Just cut out a plate, lay it on the frame to mark it and cut the frame. Tack a small piece of metal to your plate, a handle, for aid in fitting it. Spot weld it aound until you get it totally welded not letting it heat up too much or it will distort the flat area.You may have to use a body filler after grinding and sanding to get it perfect. I would probably just weld the small spot up without cutting it out.

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