I'm building a single speed bike, and ordered parts from various different places.

My EAI Bareknuckle frame got delivered this morning, and it looks great, except for this part of the fork, that has this dried brown goop on it. It doesn't look like rust, though it smells kinda metallic. I'm not a rust expert though. Or a frame/bike expert for that matter.

Have you seen this before? How can I clean it off? Water didn't dissolve it. Not sure if using soap is a good idea.

Pictures: Goop 1 Goop 2


  • It may be grease, have you tried to wipe any off with a rag? If so what was the results? How was packaged when delivered?
    – BPugh
    Aug 12, 2014 at 17:21
  • Package was wrapped in bubble wrap and newspaper and padded well. There are no dings or scratches on the frame anywhere. I tried to wipe it off with a wet paper towel, but it didn't help. It's super dried up, almost like dried paint? but flaky
    – Vidur
    Aug 12, 2014 at 17:22
  • What material is the frame made from? (My guess is that the stuff is brazing/welding flux, from assembling the dropout to the frame. It likely oozed out of the vent hole.) Aug 12, 2014 at 19:22
  • 1
    It's cosmetic and will not be seen when the wheels are fitted. Move on.
    – andy256
    Aug 12, 2014 at 21:18
  • What Andy said. It's just a rust preventative and there's no reason to bother with it. Just leave it. Aug 13, 2014 at 3:51

4 Answers 4


It looks like cosmoline which is a waxy rust preventative. It can be difficult to remove from finished parts without damage to the paint. If you can, scrape some of the heavy stuff off with something like a plastic knife. Then I would try something like WD-40. If it doesn't soften it right away soak a rag and wrap it around the fork tips over night. You can see if a hair dryer will soften it without hurting the paint

  • Yeah, I tried the wet rag overnight method and it helped a lot. I ended up having to widen the dropout a couple mm and sand a bit to get the wheel in, so I took the liberty of sanding this off. It did damage the paint, but it's hidden by the lock nuts anyway.
    – Vidur
    Aug 29, 2014 at 16:23

If I had to take my best guess I'd say it's some sort of epoxy or resin. Lord knows how it got there.

I would start by trying to get it off with rubbing alcohol. That shouldn't do anything to the paint, and might take it off. If it looks like it's helping, I'd feel free to soak the stuff for a while, it won't hurt.

If that doesn't work you may have to break out some meaner stuff, like acetone (most Goo-Off products will be basically 100% acetone) or paint thinner. both of those are really bad for your brain, though, so make sure you use it outside. They're also really volatile, so don't blow yourself up--keep it away from flames (duh) or anything that might spark, including electric motors (fans, etc.).

  • I would imagine it got there when the manufacturer put it there. It's a rust preventative for the bare metal. There's no reason to bother with trying to remove it. Aug 13, 2014 at 3:52

That's how surface corrosion (homogeneous corrosion) looks after growing beside a paint coat. I've seen several times that kind of corrosion in car panels (automotive engineer here)

Dunno what your frame material is, but you can try cleaning it with isopropil alcohol, and then cover the area with some type of grease. If the frame is too new I don't think the pitting has already covered the full thickness of the material.


As others have mentioned, it looks like a rust preventative such as Weigles Frame Saver. It shouldn't hurt anything, but if you're set on removing it you might try a rag and some nail polish remover, acetone, xylene, toluene, or mineral spirits. Take care that the solvent you choose doesn't dissolve the powder coat/paint on the fork! Two additional suggestions: (1) Make sure there isn't any dirt or grit that might damage the finish of the fork when you rub it off. (2) Don't apply so much solvent that it gets into the holes, as I'm pretty sure you want to keep the rust preventative there.

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