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Old 11-04-10, 04:48 PM   #1
Bradley P
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GT Course 853 - Rust Repair

A friend of mine picked up a GT Course 853 road bike (1998?). This bike came with an Ultegra set. I think this was a TIG welded frame and has severe rusting at the stays-to-top tube connection and also some pitting/rusting at the tube intersections with the bottom bracket. It is in otherwise clean condition. Here's an example, I can provide others:



He is riding the bike and he is not shall we say, dainty.

Is this frame toast or can something be done? I was thinking perhaps a frame strip and a bead blasting followed by silver brazing the pitted (holed?) tubing but I don't know. The rusting seems to be localized to the welded areas which makes me wonder about some deficiency in the welding process.
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Old 11-04-10, 07:14 PM   #2
unterhausen
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it just has to do with the paint not adhering as well at the joints for all sorts of reasons. No problem with the welds. I really don't know what you can do, but I would probably try an oxalic acid bath first.
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Old 11-05-10, 01:27 AM   #3
Falanx
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Quote:
Originally Posted by unterhausen View Post
I would probably try an oxalic acid bath first.
NO!

NO!

NO!

NO!

Never, *ever* acid pickling on steels over 1300MPa strength, unless you'd like to crack the remaining steel through in a few hours. No strong acids over 1000MPa, and no weak acids or alkalis over 1300Mpa. Hydrogen embrittlement, man!

You want to get that rust off safely? Blackstrap molasses dissolved to 10% in hot water. Find a nice big vessel, large enough to drop the whole frame in, and then leave it to soak for a couple of days.

But make sure you've washed any grease or dirt off first :-)
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