Internal frame rust - evil or benign?

[TTar]

I've meticulously removed every speck of rust from every little nook and cranny on a cro-mo frame. Its sparkle is blinding. What I can see of the tubes' internals though is a very different story -- they're caked with quite a thick layer of smug looking rust.

Is this anything to worry about and if it is, how do you deal with it?

[il padrone]

You can get treatments to spray into frame tubing to kill/supress rust I believe. Something like this might work well, or this one. Others may know the names of similar products.

Second point - I have a Cro Mo frame that took a few bad scrapes from about 2000 on. I was a bit over touching-up, so left them. They developed a patina of light rust and that is all - no further corrosion. The bike is still in regular use by my son. Cro Mo has about 5-6% chrome in it. Stainless steel has about 11% chrome, so this helps make Cro Mo very rust-protected

[Nobody]

Old news to some here, but I have a Giant CrMo MTB frameset that is about 22 years old and is currently still in use by a friend. I sweat a lot so the underside of the top tube looks pretty sad. I've never internally treated it and it is still going.

There is a list of things you can coat the inside of a frame with, like linseed oil, lanolin, Frame Saver, Boeshield etc. I used Lanoguard Marine & Chassis in my Surly frame before I assembled it 3 years ago. Don't know if it will make a big difference. I'm already battling some intermittent rust problems on the outside. I just repaint or keep spraying the Lanoguard occasionally, depending how lazy I feel.

[jacks1071]

Depends what the frame is worth to you but if it were valuable I'm pretty sure you can get some chemical dips done that won't effect your paint and will neutralise the rust.

Once thats done, you need to get something into the tubes that'll coat them to prevent rust from re-forming. There was some good suggestions above on possible products.

[foo on patrol]

Don't know about today but back in the 60/70s you need to be on the ball with frames that were chromed as they would rust from the inside out.

Lanolin would be my pick as you can keep giving the frame a touch up every twelve months yourself, if you were worried.

Foo

[RonK]

I always used Shell Ensis fluid, but it may be difficult to get. Just visit Supercheap Autos. They have a range on rust treatment products - you are bound to find something suitable.

[TTar]

Thanks everyone.

It's nothing special, just a rescued Nishiki Bombardier I'm tooling around with. It had nauseating purple stickers under clearcoat on raw metal. I couldn't remove those stickers fast enough and now the outside's looking pretty swish. My intention's to clearcoat the raw metal again and stay away from any stickers (especially purple ones) so I can signal passing aircraft with it's reflections.

The external rust was pronounced in a couple of spots around the lugs and there were are few minor little outbreaks on the bosses etc., but the amount of internal rust seems disproportionate -- I've glimpsed the inside of the top tube and even that is very rusty. On the plus side, the frame can double as maracas due to the noise the trapped flakes of rust make when it's shaken.

So, it's not a serious or important project -- I wouldn't want to spend any substantial amount on it -- and if I could be certain it wouldn't get worse, I'd just forget about it. I've got an old bottle of some "rustbuster" neutralising stuff that I might try to inject that into all the sneaky bits and hope I can coat all the internal surfaces. Should be a rollicking good time.

Cheers.

[drubie]

In addition to the other suggestions, you can get "fish oil" pretty cheap in an aerosol can. Last time I used it (on a good quality double butted frame) I payed a fair bit of attention to cleaning up the seat tube, the head tube and BB shell as much as I could of rust, then squirted the fish oil in every other cavity and left it to try for a couple of weeks. It will run out the drain holes (if the frame is high enough quality to have drain holes) so you need to clean it up afterwards before you paint the frame again. If I planned things better, I would have cleaned up the insde + fish oil + waited first, then sanded the frame after waiting a couple of weeks to save a bit of work.

Overall, most steel frames made since the 1980s will be pretty resilient to a bit of internal rust, although the better quality the frame the more careful you have to be because there's less steel to play with in the tube walls.

[il padrone]

It will run out the drain holes (if the frame is high enough quality to have drain holes)

Just a note about those holes - they're not "drain holes" as there should not be any water in there to drain out. They are air holes to allow heated air to escape during welding/brazing. All frames should have them. My frame was designed as a conscious choice by the makers (Thorn) to have the air holes brazed over after construction, to ensure that no moisture wold get in the frame.

If you have seriously treated the rust internally, and the frame was of a high enough value to justify it, when it is all stripped down now would be a great chance to plug the air holes in the main tubes, stays and fork blades.

[Nobody]

If you have seriously treated the rust internally, and the frame was of a high enough value to justify it, when it is all stripped down now would be a great chance to plug the air holes in the main tubes, stays and fork blades.

Another option would be to seal then pressurize the frame with a nitrogen gas feed. The bottle might be a bit heavy so you could tow it on a trailer.

[Some important metal structures are prevented from rusting by excluding oxygen in this manner.]

[drubie]

It will run out the drain holes (if the frame is high enough quality to have drain holes)

Just a note about those holes - they're not "drain holes"...My frame was designed as a conscious choice by the makers (Thorn) to have the air holes brazed over after construction, to ensure that no moisture wold get in the frame.

Interesting. I think I'd prefer to leave them unplugged to enable dry air to circulate but the air up here is never dry lately

[il padrone]

Thorn reckon, better to have no air or moisture get inside at all.

Such as having all the blow holes filled in. (These small holes are necessary when manufacturing the frame, to avoid exploding tubes!) yet they can let water in. I believe that these holes are still present in all the Americans’ frames!

A minor concern for most bikes, but if your bike was ever likely to go through flooded creeks, like my Nomad (an expedition tourer) or many MTBs, are likely to do, it's probably of value. Frame tubes with blow holes held submerged for long enough will get water inside.

[TTar]

It will run out the drain holes (if the frame is high enough quality to have drain holes)

Just a note about those holes - they're not "drain holes" as there should not be any water in there to drain out. They are air holes to allow heated air to escape during welding/brazing. .

Interesting, I always thought those little holes were there to accommodate day-to-day metal expansion and contraction.

Brazing over the holes after construction sounds pretty hardcore, why not just fill your frame with that expanding foam stuff meant to fill cavities in wall? Not only would it keep moisture out, you could float your bike across that creek!

A quick question about fish oil, isn't it meant as a preventative to be applied to rust-free metal? I should be removing/neutralising the rust beforehand, yes?

[find_bruce]

A quick question about fish oil, isn't it meant as a preventative to be applied to rust-free metal? I should be removing/neutralising the rust beforehand, yes?

Yes. use a mild phosphoric acid (the main ingredient in many rust converters) to treat the rust, rinse with water, dry, then fish oil to prevent more rust

[il padrone]

Brazing over the holes after construction sounds pretty hardcore, why not just fill your frame with that expanding foam stuff meant to fill cavities in wall? Not only would it keep moisture out, you could float your bike across that creek!

Well, by that principle my sealed-tube frame should float across already......

Somehow I doubt it

[cooperplace]

Don't know about today but back in the 60/70s you need to be on the ball with frames that were chromed as they would rust from the inside out.

Lanolin would be my pick as you can keep giving the frame a touch up every twelve months yourself, if you were worried.

Foo

"chromed" is very different to "cro-moly"

[foo on patrol]

Don't know about today but back in the 60/70s you need to be on the ball with frames that were chromed as they would rust from the inside out.

Lanolin would be my pick as you can keep giving the frame a touch up every twelve months yourself, if you were worried.

Foo

"chromed" is very different to "cro-moly"

I know that and wasn't talking about cro- moly tubing.

Foo