sherbornpeddler

Now these are interesting suggestions!
Do you think foam migt accelerate corrosion of the steel tube? Could it cause corrosion or is it really inert?
The pliers look very cool.

sherbornpeddler

Suggesting the reason for not using grease is chemical?
Anyway my Serotta Fierte has a glued carbon backstay. I was afraid of powerful penetrating oils when I was trying to remove the broken post.

I think the anti-grease crowd chant it makes it slip leading to over tightening and fracture of the post. The greasers have grease that inhibits corrosion without being too slippery.

Panthers007

Regards the blown-in foam insulation - no need to buy it. The chemical in it is methylcellulose. Which has two purposes in the market*. One is as insulation as mentioned. The other is to thicken McDonald's shakes. Just leave one out sometime - you'll see! So you could pour a shake down the seatpost...

* A friend of mine was friends with the guy who invented the muck.

sherbornpeddler

Now this is what makes forums great: invention, information, imagination and humor. I wonder what flavor would work best and if I could retrieve it if I ran out of gu?

kwrides

Sorry to bring back an old thread. I have a 1 month old carbon fiber seatpost stuck in the aluminum sleave of my carbon fiber bike.

The seatpost is FSA and I slathered their compound on it before insertion, but it is now stuck firmly in place, so don't count on this to be your solution.

I'm willing to sacrifice my seatpost and will be going back to aluminum, but am weary of taking a saw or drill to the bike myself. My LBS (not where I bought the bike) doesn't want to work on it and told me to call FSA. FSA doesn't answer questions like this on the phone and forces you to email them. It's been about a day since I sent it and no reply yet, but I will post the reply and/or solution once I get it.

Does anyone know if you can use coca-cola or solvents in a CF frame?

Also, I'm new to the Mechanics forum. Would I be better off starting a new thread with a CF seapost/CF bike header?

Thanks in advance for your help.

sherbornpeddler

Again wonder what is it in carbon posts that is reacting? Ain't the carbon so it must be the epoxy itself.

Pocko

Some years back, when I was doing some research prior to making a custom carbonfibre frame, I came across an article (can't find it now) about - carbon and aluminum in contact with each other, being a bad combination. Something to do with electrostatic-corrosion... hence areas within the carbon frame that needs "bonding" to aluminum sections (threaded BB sleeve insert, Headset Bearing sleeve insert, aluminium Dropouts, etc) should be first wrapped or laminated with fibreglass, and then carbon - the fibreglass acting as an electro-static insulator. Without the fibreglass, given time, the bond will fail.

It is my understanding that it is the aluminum that corrodes (not the carbon or epoxy).

If this principle applies to seatpost problems, one would think that the post would loosen instead of tighten... unless the aluminium corrosion (white powdery rust) swells into the fit when moisture or water is added into the mix... purely hypothetical reasoning at this point, sorry to say...

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Pocko

Oh, I forgot to mention... according to the article, a carbonfibre frame generates "static" when air rushes past it... just like running a comb through your hair...

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BrooklynTrack

Yo honestly I just got the best idea. Pour gas down the seat tube (obviously have to remove clamp) then light that son ofa ***** on fire, the fire should shrink the carbon, or incinerate it enough to get it out.
Granted, a terrible idea, but you could try it.

joejack951

That's exactly what happens. It's also how many fasteners (typically steel plated with zinc going into aluminum) corrode and sieze causing the fastener to break off during a removal attempt.

sherbornpeddler

Now that is an idea. I could try a soldering gun and melt or soften if not incinerate the epoxy.

MarkWW

Well to remove your section of carbon post, sherbonpeddler, I would flip the frame upside down with the current seatpost out. this should cause the section to fall down until it hits the butted section of the seattube. Then you could insert a long enough pair of inside measuring calipers so that the hooks are just past the section of seatpost. Then with a sharp tug, they should be able to pull the bit of seatpost out. hopefully.

Pocko

Yep, bi-metal corrosion... and apparently it's particularly bad with titanium frames around areas where it touches other metals like steel BB bearings, pressed headset bearing cups, seat post...

With carbon against metal, it's electro-statics that apparently causes the corrosion. I was talking to a boat-builder about this some time ago and he says composite powerboats have a similar thing going - where the water (salt water in particular) rushing past the surface of the hull causes static elctricity and corrodes the heck out of submerged metal parts (rudders, propellers, etc.). What they do is bolt these brick-sized zinc blocks at the back of the boat (underwater) as a sacrificial offering to the static-gods so that vital metal parts would be spared. A 40 foot boat can eat up two of those zinc blocks within a year... he had shown me the remains of used-up zinc blocks!

Could be what's happening between the carbon seat post and aluminum seat tube, to a lesser degree... could be..

Unverified information here, just making conversation as one does in a forum...

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Nessism

Electro-static? You sure? I've heard of galvanic corrosion, which involves the migration of electrons between materials of varying electronegativities, but never heard of electro-static corrosion.

Regarding the seatpost sticking, I had this problem with a Campy carbon seatpost a few years ago. The paint on the post is what caused the problem. After levering out the post I scraped off the clear paint below the frame insertion mark and the problem never happened again. The epoxy coating over the carbon is quite inert and makes a good surface to put against just about any metal; the carbon doesn't actually touch the metal for the most part other than maybe in small localized areas where the fibers poke through the epoxy coating. And grease typically doesn't attack epoxy although I understand the hesitation. Grease on a seat post, made from any material, can cause slipping which in part requires more tightening pressure. It's the high claming pressure that can destroy the carbon seat post, not chemical attack by grease.

joejack951

I couldn't remember the term (my mind must be going) but, yes, the issue is galvanic, and not electrostatic, corrosion. I work in the marine industry (though not on boats directly, I design products used on boats) and all of the saltwater boats (power or not) that I have seen have the big zinc ingots bolted to the back of them to stave off corrosion. The corrosive elements in the water like to take the path of least resistance which happens to be the nearby zinc rather than the other submerged metal on the boat (typically bronze or stainless steel).

Pocko

No sir, not sure... hoping to learn thru discussion, glad and grateful for your contibution...

So, not applicable to the topic then.

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joejack951

Some good, basic stuff on corrosion (does not address carbon fiber though): https://www.engineersedge.com/corrosion.shtml

sherbornpeddler

In my case the steel seat tube may have rusted causing iron oxide to work it's way into very small pores of the carbon fibre seat post epoxy. A bit of a tangent but I've heard of carbon seatpost and carbon seat tube becoming stuck.

Best solution seems to be a monthly loosing and repositioning of your carbon seatpost. For the present I am using an inexpensive Al seatpost, with grease, clamped up tight.

sherbornpeddler

Mark, great thought. I may combine that technique with others. The attached illustration may explain why I've not been able to pull it out. The busted, peeled end (aka Bart's hairdo) of the post facing the butted section exit is splayed out. It was a very snug fit before it broke so the added fragments won't let it out unless I cut, melt, file it into pieces. I already shopped for a cut-melt-file attachment for my dremel but haven't found it yet.

khearn

How about using a propane torch to burn the seatpost? I don't know how hot you'd have to get the seatpost before it burns, but steel can take a lot of heat before it starts changing properties. Do it in a semi-dark area, and if it starts glowing, stop applying heat. It'll mess up your paint, though. I don't know for sure if it would work, but it's an idea.

Do you still have any of the seatpost that you removed? If so, you could find a junk frame and test it out. A propane bottle and screw-on torch head cost less that $15 last I checked.

Definitely avoid breathing the fumes.

Keith

Nessism

I still say it's the clear paint used to make the seat post shinny that is causing these carbon seatposts to stick. I know most of you guys would freak out about this but scraping off the clearcoat with a single edge razor blade on the portion of seat post that fits inside the frame works well.

kwrides

For those who care about Customer Service, it's been 2 days now and still no reply from FSA. I ended up taking it to the shop where I bought it and they're giving it a shot. I will definitely be buying an aluminum post there too.

sherbornpeddler

End of long story. I rode with the broken piece rattling until a week or so ago. Since then I ptuzed, hummed, hawed and tinkered. I tried sawing with an ohmmeter so I could tell if the blade contacted frame. It works but what a hassle! I adapted a vacuum for health and visibility. A simple hook with a bungee worked best to hold the broken post in place while sawing made from 3/16" heavy wire; a little short so it didn't quite stick out of the seat tube. This way I could pull it tight off to the side with a string to a bungee. Too short and it is a nuisance to fish down and hook the bottom of the post.

I tried single and double hacksaw blades, a carbide tile saw blade, several files and finally hack saw with Sawzall. The double hacksaw blades flopped around the least; the carbide saw (for ceramic tile) cut the carbon best. Frequent vacuuming and light adjustment were necessary to see what I was doing.

What really helped was stuffing an old blade (green in my drawing, dull red in photo) between the "hooked" broken post and my precious Serotta steel seat tube. The old blade became a protective layer distinctly different than the carbon post. In the photo it is shoved aside; while cutting it was directly under the path of the saw blade. I cut the initial groove by hand then did the bulk of the cutting using a Sawzall with the carbide or hacksaw blades. I did the final cuts by hand.

I cut the post in two with not even a scratch on the seat tube ID. The Rattle is gone!!!!
I am using aluminum, greased seatpost.
Folks, Thank you for your ideas and support.

Pocko

^ Man! I admire you for your patience and anger management prowess!!

mlts22 

Wow, you deserve some type of mechanic's war metal for doing that. I would have run out of ideas long beforehand.