How can you tell if a frame has rusted inside?

[Alpha1653]

Apologies if this has been asked before but I've not been able to find a thread about it elsewhere.

I'm trying to build up a 1997 Kona Cinder Cone but was wondering about internal rust. Externally, there's no signs of rust but as far as I'm aware, the insides of the tubes were never treated to prevent it.

If it wasn't treated whilst being constructed, what are the chances of the tubes having rusted from the inside whilst showing nothing externally? The frame was ridden from 97 through to about 2000 but then got stripped and has been hanging in my garage.

Obviously, looking inside the tubes would be a good plan but the holes are so small you can't see anything.

Any ideas?

 

[highlandsflyer]

You can see inside enough to get an idea, then you could spray in some WD40, for example and see what runs out.

 

[Raging_Bulls]

I'm thinking along the lines of a miniature camera, but no idea where you can have it checked out with one.

However the seat tube should be a good indication. Take the seat post out and use a flashlight to look inside the hole.
If there's rust in there, there's a chance that there is rust inside the rest of the tubes. If it's clean, the chance is a lot smaller.

 

[Alpha1653]

Thanks for your replies. I think I'll try the WD40 trick tomorrow. The seat and head tubes are clean so that's a good sign.

I'm probably just being paranoid!

 

[feetabix]

remember rust itself is a very stable medium, and will protect underlying steel to a degree.....so long as the frame hasn't sat with water inside for too long it should be fine.....i think any used steel bike will appear with internal surface rust, but ive never had one rusted to a degree that compromised its use.....im a right fatty too, so i should know!.... :roll:

 

[feetabix]

have a tap around its nether regions with an allen key, surely any rotten areas will sound unusually dull?.....

 

[pete_mcc]

Shake the frame, if it sounds like Bez's maraca then its f*cked. Normally though, if a frame looks abused on the outside then fear for the inside.

 

[Thunderchild]

A borescope or boroscope would work. It would need to be long enough to reach the depths and narrow enough to go through the holes between bike tube sections. i am not saying it would be better than other suggestions. I have used them to look in walls for water damage.

THunderchild

 

[AMPrider]

Use an LED flashlight($2.00 at Dollarama here in Canada). They are intensely bright and will light up the insides of the tubes well enough to detect rust.

 

[FST4RD]

2 things...
If it's like my '93 DB Apex just ride it until the frame snaps and hope it's a seat stay, that's what happened to mine.
Other thing is, go buy some POR15 or fish oil and pour it into the frame and shake it really well to make sure it gets everywhere. This is more of a future proofing option. Fish oil should stop further rust from growing, but it smells. POR15 will convert rust to an extremely hard metal again and rust will never grow again as long as you managed to get it everywhere inside. Get it on your hands or skin though and you won't get it off (there's a warning on the car that says "only time will remove" ) If you can get a compressed air spray gun with a long flexable nozzle you can then get it down the tubes and through small holes.
Good stuff though, I used it when I found some rust in an old car I used to have.