[Closed] Anyone seen this happen before?

Don't really need any press articles to prove galvanic corrosion problems. This is 1st year engineering: http://en.wikipedia.org/wiki/Galvanic_series

The further apart two materials are in the series the higher the risk of corrosion when in contact with an electrolyte to complete what is basically a cell. The principal is used in zinc galvanising as the zinc is lower in the series than iron/steel it protects any exposed steel (and the intact zinc protects as it's a physical barrier).

The carbon fibres in CFRP are graphite which is right at the top. Aluminium is right at the bottom.

If the fibres are coated with epoxy it is less of a problem but you get exposed bits of carbon and epoxy does absorb water. It would be pretty safe to say there will be exposed carbon and aluminium in contact with an electrolyte in this bike seat tube situation and in this case the aluminium is the one that suffers. Which is good really otherwise the frame might be trashed.

My mate gave me his bike to sell a few years ago and his post (when I eventually managed to get it out!) was like this too.
It was his winter/summer training bike.
[url= http://donder.co.uk/?p=434 ]As above, its Galvanic Corrosion.[/url]

Which component of Carbon, causes this?

The carbon fibres themselves - in most applications the resin will form a decent barrier as will any anodising. I guess that the seatube is either mandrelled during manufacture, and/or reamed afterwards which could expose the fibres. If the post is moved up and down it might scratch the anodising exposing bare ali to the naked fibres, a bit of salty water (from washing with soap?) and you've got a battery!

this thread is well interesting now, good work all.

"Don't really need any press articles to prove galvanic corrosion problems. This is 1st year engineering:"

Indeed it may be 1st year engineering, however you may be surprised that not all people contributing to, or reading posts on this forum have studied engineering in any capacity. Some of these may appreciate a reference to a press article aimed at the layperson.

Indeed it may be 1st year engineering, however you may be surprised that not all people contributing to, or reading posts on this forum have studied engineering in any capacity. Some of these may appreciate a reference to a press article aimed at the layperson.

Exactly it's a general discussion, although I've got a BEng, other might also be interested and as people who work or deal with this specific field appear to be posting, they may post some other interesting links/finds not in a wiki entry, any posts on suspension tech stuff I'll always try and make it understandable anyone who may read it 😉

so, you need an electrolyte in there to set up the corrosion?
what could this be, apart from water? mud? salt?

I was just saying that there was no need to worry about finding press articles (not always the best source of reliable information) when it's best shown with firm scientific fact that anyone in the field would be able to point you in the right direction of. Although evidence of the science bit causing problems in the real world are always useful.

brakes - the electrolyte will be exactly what you have listed. Just impure water with contaminants already existing on the parts, the users hands and the environment the part is used in.

LoCo I would not worry. cheif9000 is just a serial googler like the rest of them..

"Can I quote you on that?"

I can probably provide you with some references more if you need.

The next challenge you face is deciding what you want and getting it. what is your desired outcome? It might take some time.

I'm not fussed, I was just joking really 🙂
Remembered I had a nice RaceFace post that fits sitting in the garage, which is handy as the frame is sold and the post was included. I'm REALLY glad I spotted this before I sent it!

toys19, I was being lazy too otherwise would have posted a relevant link 😉

Poddy, hope they don't find this link and want you to retro fit the glass barrier on the inside of the framae as part fo the deal 😉

Interesting about the internal surface finish of the frame, would have thought they would have sleeved in some way 😕 Will ask someone who knows a bit about carbon ex Nascar current F1 engineer friend.

The On-One post you photographed the bike with? 😉

[img] [/img]

Interesting about the internal surface finish of the frame, would have thought they would have sleeved in some way Will ask someone who knows a bit about carbon ex Nascar current F1 engineer friend.

no sleeve from what I have seen on my C456. Tbh if the risk was to the frame then it would be worth it (eg any aluminium fittings such as BB and headtube inserts) but I suspect the cost v risk/benefit doesnt add up on these frames at this price point. No sign of any problems on mine in two years.

As long as the post is greased with an appropriate compound this is not a problem and the frames don't need special treatment to allow for it.

It's PP's penchant for going in dry that's the problem, not the post or frame design.

As for the 'no instructions' thing - I quite like the Ragley "If you have to ask how to fit this component properly then get a bike shop to do it" 😉

I was meaning in general material terms not specifically bikes or On One, I'm sure Brant and the manufacturers would have taken this into account.

It's PP's penchant for going in dry that's the problem

😯

*whistles innocently*

With regard to greasing carbon frames or posts, I was lead to believe that due to the construction of carbon, it's not perfectly round. This allows grit, water, etc to get between the frame and the causes the corrosion. If unchecked it can seize. That's why I've used carbon assembly paste on both my C456 with its carbon post (which slipped without the paste) and my ASR5C (Thomson post). The Thomson didn't slip, but I've used the paste to try and keep the muck out

It's PP's penchant for going in dry that's the problem

I was meaning in general material terms not specifically bikes or On One, I'm sure Brant and the manufacturers would have taken this into account.

C456 nothing to do with Brant and I wouldn't assume the manufacturers would do anything for this situation. There are aluminium rivets holding on cable guides and people attach aluminium clamps to carbon frames and bars and your aluminium BB and headset cups can still be bridged by moisture. It's just not normally a major problem on the most part either due to rarity of occurrence, severity of effect and extremity of conditions.

It PPs case it looks like it has either been unlucky with an effective electrolyte trapped there (eg i can see water + bike wash being a very effective one) for a while or a defect with the aluminium part making it more susceptible (thin anodising, poor structure etc) but that's not my field to comment on.

But on the non-bike related case yes you are correct. One would normally take measures to prevent this kind of thing. Normally through choice of materials or through protective barriers either between materials or preventing moisture/chemical exposure etc (eg sealants used to protect exposed fasteners on aircraft )

"If you have to ask how to fit this component properly then get a bike shop to do it"

I am, actually, now a qualified bike mechanic....... 😉

I'm also not 100% sure it's the same thing as in the link about 'galvanic corrosion' either. There's no sign of and corrosion on the surface at all.
Like I said, I'm not fussed. It's going in the bin, I've found a replacement and I doubt the manufacturer will answer my email. They didn't answer my last one related to purchasing spares for one of their items.

On one, enough said

PeterPoddy - Member

"If you have to ask how to fit this component properly then get a bike shop to do it"

I am, actually, now a qualified bike mechanic.......

😯

Final update:

I pretty much accept the post should have had carbon paste on it and its probably my fault but I did show it to a vastly experienced mechanic at ATG who train cycle mechanics and he wasn't 100% sure. Anyway, they now have it as a training aid! 🙂
The post was an On One post. They never bothered to reply to my email, just like they never bothered to reply when I enquired about headset bearings for the same bike. This is the same bike with a head tube too short for some tapered forks and a step in the headtube that prevents easy headset removal. The advice being to twist it out in a vice. Yeah, OK.
To be frank, I'm sick and tired of their poorly designed and untested frames. I'm sick and tired of fixing the faults. I'm sick and tired of being ignored. I've had 3 frames off them over the last 5 years and a fair few parts, but I'm not buying any more. They've lost my custom permenantly now. This is a pity as the bikes ride well. But then so does my new Saracen.
I'll keep my 853 Inbred because that's OK since I fixed it's main fault with a new chainstay and its a tough and versatile frame, but that's it. 🙁

So there! 🙂

Some do have a glass ply in there some don't can usually sort the good factories from the bad a lot of higher end comold instad of using aluminium inserts now...for a number of reasons
i know a lot of them overseas folks still refer to black fibreglass on their layup shedules so its very easy to put that in the wrong place on a Friday afternoon

@compositehero.... Did you use a random word generator for that or is English not your first language? 🙂

no just have a poor grasp on grammar and typing stuff on phones

im good with numbers thankfully