Titanium frame has a crack - advice needed I've found a Titanium bike frame on eBay. It's very cheap and the owner says that it has a very small crack on the seat tube where it connects to a bottom bracket. See in the image above:

I've never gone for titanium frames. How bad is this damage, and what is likely to happen in the future - will it get worse?
If you look at titanium frame bikes on the web you can see their warranties. Most have very long or life time warranties that cover everything but crashes and deliberate damage to the frame. So I would assume this frame was involved in a crash.

There are three types or cracks in titanium frames (from best to worst):


Weld crack
seam crack (titanium comes in sheets that are bent into tubes and seam welded.)
Stress crack


You can weld titanium (but you need an inert gas shield to prevent O2 &amp; N2 absorption while the material cools). Seam and weld cracks are relatively easy to fix. (But still pricey.) A stress crack may not be repairable at all, and I'm not sure I would trust it in any case on the BB.

So without anymore information, I would say you have a crashed frame with frame failure. It is in the worst possible place. A repair will be expensive and may not even be possible. The repair was also not covered under the frames original warranty. 

After looking at the crack again, there is another possibility. When you weld titanium you have to shield the metal with an inert gas as it cools. Otherwise it can absorb O2 or N2 from the air. If the titanium absorbs either gas it becomes brittle and will crack over time. This crack is right near the BB at the seat of two major welds. The tube would have been very hot there and if it was not properly shielded by argon during welding and cooling, it could have absorbed air during that period. That effectively wrecks the titanium. This type of problem can not be fixed. (It should have been covered under warranty though.)

Sounds like a good frame to avoid no matter how cheap the price.