Old 04-16-12, 11:50 AM
  #11  
scotch
purity of essence
 
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Join Date: Feb 2006
Location: NH
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Bikes: 2018 Giant Trance 2, 2019 Trek Farley 7, 2017 Jamis Renegade Exploit

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Originally Posted by Chombi
I suspect that the dissimilar metals (threaded insert and frame tubing was reacting to each other from moisture induced electrolysis. Only way to stop or slow down the corrosion on the aluminum tubing is to clean off the corrosion and repant the area to seal it up so moisture cannot get at it. Now that the paint is compromised in that area. the corrosion will just keep going and probably accelerate as the bubbling and flaking paint will keep trappng the moisture against the frame tubing.
I suggest at least removing all the corrosion and a repaint with a matching automotive spray can paint with a coats of clear to seal the paint for a long term fix.
If you are not up to re-painting, it might actually also be better to take off the paint where you see it bubblng up and clean off the corrosion with maybe some Scotch Brite pad and WD40s till you hit bare aluminum then just give the exposed aluminum areas a spray and wipe with WD40 everytime after you ride the bike in the wet If corrosion starts again, you can just hit it again with some Scotch Brite pads to take it off.

Chombi
Thanks, Chombi, for all the feedback. The more I think about it, the more I like the idea of at least having that entire section of the tube re-painted. Then I think, well, I've never really liked the paint job on this bike anyway, so why not have a pro just repaint the entire frame.

At the very least, I think I will deal with the corrosion down to the bare alum and repaint that section.

Originally Posted by bobn
Strange that the insert doesn't have any oxidation. As mentioned before, check it out with a magnet.
Your idea of taking it to a pro is a good one. You may have to remove a lot of the paint to see how extensive the corrosion is under it. If it's not to bad and safe to ride, you can paint a black ring around the area. Kind of a custom job rather than trying to match and blend the paint. You can do that yourself with a little masking tape and a rattle can color of your choosing.
Thanks bobn. I'm going to check the holes with a magnet and I'll report back what I find. The good thing is that this is the under-side of the downtube, so it's not super visible if I end up doing my own work.

Cheers.
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