Preventing Internal Frame Corrosion

KonaKurt

i got chatting to a mechanical engineer about mountain biking and in particular hardtail bikes, such as mine. He told me that even with Aluminum frames, internal corrosion can occur over time, especially if like mine, your frame has any small 'airflow holes' pre drilled in the frame, to allow the material to 'breathe' (most Kona hardtail frames have these holes). He also mentioned that it is possible to protect internal frameset surfaces from a risk of corrosion or deterionation, by using a simple technique of injecting a foamy substance inside the frameset, in a simular way to how your cavity walls are done to your house.

Anyone got any idea what he was on about? He wasn't exsactly sober as he told me this, so not sure if I should beleive it!

KK.

abarth_1200

I thought aluminium wasnt that badly affected with corrosion.

Something to do with a layer of oxidised aluminium forms on top and protects under it

KonaKurt

Abarth, that's what I thought too. But he might have been talking more long term, say over 20 years or so.

Anyone heard of any such treatment?

KK.

ratty2k

Wouldn't bother, in 20 years, you'll more than had your moneys worth.... The "airflow for breathing"? WHAT??? So air can escape during the welding process.... I think your engineer is talking BS myself. There are waxy treatments for steel frames, but even they dont suffer badly enough to worry about either.

Atz

It's not a significant risk. You're far more likely to crack a weld, break a tube, ruin a chainstay because of chainsuck etc than rust a frame from the inside.

amt27

when I did material selection at uni, the lecturer showed us an example of salt corrosion on an aluminium seat post,

someone had put tape on the post to mark the height, dirty water had gotten trapped under the tape, water evaporated and the salt corroded the post, resulting in it snapping,

nicklouse

amt27 wrote:

when I did material selection at uni, the lecturer showed us an example of salt corrosion on an aluminium seat post,

someone had put tape on the post to mark the height, dirty water had gotten trapped under the tape, water evaporated and the salt corroded the post, resulting in it snapping,

did the Lecturer state the time scale of this?

Uncle Peter

ratty2k wrote:

Wouldn't bother, in 20 years, you'll more than had your moneys worth.... The "airflow for breathing"? WHAT??? So air can escape during the welding process.... I think your engineer is talking BS myself. There are waxy treatments for steel frames, but even they dont suffer badly enough to worry about either.

I think the holes are for allowing hot air/welding gases to to escape during welding? The heat makes the air expand wich I guess they believe could damage/weaken the frame/weld.

BorisSpencer

I thought the aluminium oxide formed a protective layer preventing further oxidation taking place. So as long as you don't keep polishing the inside of your tubes you should be okay.

amt27

nicklouse wrote:

amt27 wrote:

when I did material selection at uni, the lecturer showed us an example of salt corrosion on an aluminium seat post,

someone had put tape on the post to mark the height, dirty water had gotten trapped under the tape, water evaporated and the salt corroded the post, resulting in it snapping,

did the Lecturer state the time scale of this?

can't remember, probably a number of years, I used to do that same myself

butcher of bakersfield

I recently got my hands on an alu frame and there's visible corrosion around the mounting holes - bottle cages etc. I'm not worried about it, but it is there. It's about 6 years old.

Generally steel (cro-mo) doesn't corrode either, if you look after it well. It used to be well regarded for that, before the days of alu...but it does corrode.

ratty2k

Uncle Peter wrote:

ratty2k wrote:

Wouldn't bother, in 20 years, you'll more than had your moneys worth.... The "airflow for breathing"? WHAT??? So air can escape during the welding process.... I think your engineer is talking BS myself. There are waxy treatments for steel frames, but even they dont suffer badly enough to worry about either.

I think the holes are for allowing hot air/welding gases to to escape during welding? The heat makes the air expand wich I guess they believe could damage/weaken the frame/weld.

Not a welder by trade, but can weld as part of my job, I think the hot gasses will blow through the pool of hot metal on closed end tubes, not good...

KonaKurt

I just found out that the 'engineer' I was talkingto beforehand, is in fact a retired plumber!! He knows nothing about bikes at all, so ignore his suggestion about internal protection.

Personally I agree, that worrying about breaking the frame or it's welds is more a concern. Besides, most framesets come with a 'lifetime' guarentee, don't they? And as for injecting a substance inside a frameset, surely it will eventually ooze back out making a right old mess in the process!??

Depending on the exact alloy and grade of aluminium, salt can corrode it within a few years, but I generally avoid saltwater and coastal areas anyway.

KK.

ratty2k

Engineers, all bollox. I'm a fitter and have spent twenty odd years fixing engineers feck ups.

forcutty

ratty2k wrote:

Engineers, all bollox. I'm a fitter and have spent twenty odd years fixing engineers feck ups.

Machinists say the same thing about fitters and designers

snotty badger

ratty2k wrote:

Uncle Peter wrote:

ratty2k wrote:

Wouldn't bother, in 20 years, you'll more than had your moneys worth.... The "airflow for breathing"? WHAT??? So air can escape during the welding process.... I think your engineer is talking BS myself. There are waxy treatments for steel frames, but even they dont suffer badly enough to worry about either.

I think the holes are for allowing hot air/welding gases to to escape during welding? The heat makes the air expand wich I guess they believe could damage/weaken the frame/weld.

Not a welder by trade, but can weld as part of my job, I think the hot gasses will blow through the pool of hot metal on closed end tubes, not good...

Yup, bloody annoying too. Also having the holes prevents pressure build up in the tube which can weaken the weld even if it doesn't pop!

Barteos

Based on my own experience all I can say is that most of engineers are so highly qualified experienced and knowledgeable, that when it comes to such simple things like bikes, they become strangely confused and as a result they talk gibberish.

KonaKurt

Barteos wrote:

Based on my own experience all I can say is that most of engineers are so highly qualified experienced and knowledgeable, that when it comes to such simple things like bikes, they become strangely confused and as a result they talk gibberish.

I completely agree, and notice this alot. Cycle technology seems to be utterly pointless and overdone I dare say, in the eyes of many engineers. I also dare say that for many non-cyclists, cycling technology is 'pointless fussing' (as a grumpy member of my family often says to me!).

Mind you, at least my plumber pal had his heart in the right place and genuinely tried to help with a bit of applied science - which is more than many so called bike shops I have visited have bothered to do!!

KK.