flipchip

Am I right in assuming this is galvanic corrosion, and just how bad is it?

Iride01 

Are you certain it's not just dried up sweat or spilled drink?

The stuff doesn't indicate the bike is unsafe. Even if it's a problem the bike likely isn't going to fail anytime soon, nor will it fail spectacularly.

maddog34

the "white powder" is Oxidized Aluminum.... the epoxy bond between the aluminum lugs and the carbon fiber tubes will be violated by the growth of those disorganized crystals. At some point, the bond fails completely.

the oxidation has even gotten between the CF layers and the Epoxy on the tubes.

How lucky do you feel?
The area imaged is a very critical area on a frame... Frame component separations at the steering head lead to major dental repairs, scars, and sometimes death.
Is your insurance paid up?

How long did the bike remain out in the weather?
Control cables will be another failure point to watch closely.

Famous Last words.. "Oh CRAP!"

i'd imagine that a search of these forums will bring up a few threads on "Aluminum/Carbon Fiber Frames Separating"...... I know Trek warrantied a few hundred of the composite frames... ALAN had a lot of Oxidation failures too, and that was Aluminum/Aluminum bonds... a still active thread is discussing Failed Bonding between Aluminum/Aluminum. the possible culprit appears to be.. yep.. Oxidation from water intrusion lifting the Epoxy bond, and that then weakens the structure, and cracks begin to form........ etc.

Here's a response to a guy that bought a used Allez CF/Alu frame... "

RC28

· #18 · Mar 21, 2011 "Watch out for galvanic corrosion at the lugs. I know several people who sent their frames for warranty replacement at the time (1994 I believe it was) because of this."

the other responders only spoke of their enjoyment of the frames...

the failures have a history dating back to the earliest releases, and that history began not long after the introduction...

TiHabanero

Yep, galvanic corrosion going on in there. Eventually will fail, sometimes without warning. The Trek 2300 I had did this, except I let it go much longer than you have here. Was still holding together when I got rid of it.

Kontact 

You would have to have a deathwish to ride a bike with failing head lugs. If one of them goes, you are tasting pavement instantaneously.

I think it is safe to say that this Allez model is the single worst composite bike for bond failures ever commonly sold. I have seen dozens of these come apart over the years, and all with the powdery evidence of galvanic corrosion.

Which is really crazy when you consider how well the various French composite bikes have held up. Specialized obviously skipped a step in the design/assembly of this model.

Andrew R Stewart 

Back in this bike's day Specialized glued carbon tubed bikes did get a reputation for this very issue. The really bad ones would show this after a season or so. The company told us dealers that there had been a bad production batch where the BB shell wasn't properly prepped before assembly, I've seen a couple of these with serious chainstay/shell white deposits. One of the lessons/tasks I would teach the new mechanics was to wipe off the frame and run your fingers over the tube ends, checking for "stuff". There's a reason why the bike industry started to shorten their frame warranties as the frame materials drifted from steel.

IMO this frame has proven that it was constructed better than needed to survive for longer than warrantied. It was pretty close to the leading edge in a production model for it's time coming from a manufacturer (Giant) who was still early in their learning curve.

I would continue to ride the bike and routinely do a frame wipe off and exam. The images don't show the concentration of corrosion right at the joint edge, as in what I saw in the worst cases, that gives me pause. But I also consider this to be the hand writing on the wall. Start the replacement planning and do that when that time is right. Andy

Mr. 66

I would put on oil the spots sand if needed, polish, wax. Eliminate the catalyst if that's possible.

Kontact 

It's not possible. That isn't how galvanic corrosion works and this frame is beyond being safe.

Zara Sp00k

My 2300 has never shown any evidence of this. Nor my 8700 . Both bikes are over 25 years old with a lot of use.
I wonder if there is a cause beyond faulty engineered/manufactured product. Something like ocean side environment, outdoor storage, or something.
No doubt some brands were just poorly engineered or assembled. Properly done, this should not occur.

Kontact 

It happens when the builder doesn't electrically isolate the carbon from the aluminum via a layer of fiberglass or the equivalent, and then it gets ridden or stored in damp conditions.

I think some bikes didn't have the fiberglass, but the way they were glued worked reasonably well to prevent much contact. Hard anodizing of the lug my have moderated the effect as well.

I would bet that the Allez, which were slightly unusual for having external lugs, required internal sanding of the lugs to get a decent glue gap, and that left the aluminum totally unprotected and electrically active. Almost everything else from that era used a beveled slip fit into an internal lug, like the Vitus, Giant Cadex, Trek 2300, etc.

maddog34

oil will speed up the bond failure.... but it sure will LOOK better until it fails, eh?

mpetry912 

I don't like the look of that. Risk of injury from catastrophic failure is significant.

And it will happen at the worst possible time ! like hard braking going downhill.

I have a bike with similar construction - Serotta Ottrot. It seems very solid but these bonded joints can degrade over time.

Especially if you live near the sea, salty air will do it.

Others can speculate based on what they see in the picture. I would not ride that bike

/markp

Mr. 66

Lol, I really don't think oil will do that. The bonding agents shouldn't be affected from that.

mpetry912 

when it is sufficiently degraded so as to be putting out an oxide as shown in the pic, it is hard to tell what might and might not happen.

As Andy pointed out, there's no concentration of oxide right at the lug boundary. however it might have been wiped off before the picture was taken.

There is a risk of failure anytime you ride a bike ! or fly an airplane. I take that risk with an understanding that I've done everything possible to reduce and mitigate the risk.

However I would not be assured by speculation from the list members (however knowledgeable) based on one picture. The downside consequences of the risk eventuating (in this case, frame failure and resulting crash / injury) are just too great.

But what do I know ?

/markp

Kontact 

A correctly insulated joint would not be affected by salt or much else. The bonded part of the aluminum would be the last part to corrode because it is slathered in epoxy. This only happens because the aluminum and graphite are directly touching to form a circuit.

The bonding agents have already failed, and some of the joint is being held together more by an interference fit from the expanded aluminum oxide than an actual bond. Introducing easily wicking oil is an invitation to wash that aluminum oxide dust out of the joint faster than it would normally. And it certainly isn't going to decrease the electrical contact that is already occurring and causing the corrosion in the first place.

mpetry912 

if what you say is true (and I'd be inclined to say that it is) then the bike should not be ridden period.

Tell me if you don't agree !

/markp

Kontact 

My first post in this thread is strong warning that this bike could kill the rider. When that downtube comes loose that frame is going to fold like a beach chair. It is only a question of when, not if.

fishboat

I have a '92 Trek 8900 that's now..31 years old and it shows no evidence of this corrosion. I read somewhere, can't remember where, before I bought this bike that Trek used the same process-procedures bonding the aluminum lugs to the carbon tubes as the aircraft industry(or maybe that process is just good-practice known at the time). My condolences to the OP, but it is good to see what this corrosion looks like. I did a ton of research on carbon/aluminum lug frames prior to purchasing the 8900 and didn't come across a discussion like this. Hopefully this discussion will help someone in the future.

..just looked at the 1992 Trek Spec Manual and found this:

wheelreason

Don't quit your day job.

Atlas Shrugged

The cloud has moved on or in their case the OP has ridden on.

Kontact 

Just answering mpetry's direct question.

I'm sure the OP has not enjoyed what he's read on this thread.

Mr. 66

lol, lots of speculation in this thread.

Kontact 

Some of it cautious, conservative and safe. Some of it ungrounded and dangerous.

Not equal.

stevel610 

My first thought was duct tape. You could a piece (or two) along the right side of the top tube, around the head tube, and down the left side of the top tube.

Then take a long piece and wrap around the top tube over the other piece, like you wrap handlebars. Don't think it will really keep the head tube together, but you'd have plenty of tape to imobilize broken limbs after the crash. 🤪
https://www.bicycling.com/repair/a20...ith-duct-tape/

Atlas Shrugged

7 posts to answer the same question?