[golgiaparatus]

Well as some of you know I have been waiting for an ebay purchased bike to come in. Well it finally did. I was looking it over after assembly... Looks pretty good... rear wheel need truing, no biggie, needs an adjustment here and there. Components are all good, tires brand new expensive Hutchinson models, chain clean as hell, etc, etc. I was looking at the housing wich looks a bit old, again no big deal. But as I was inspecting it I noticed where it runs against the top tube one of the fasteners has paint all bubbled up around it... I thought this was a bit odd. It looks like rust under the paint. When I started scratching at it with my fingernail it just flaked off paint and all. It looked like calcium build up. WTF is this from and what should I do about it? Anyone dealt with this before? Personally I have had a number of aluminum frames, but I have never seen this.

 

[Westy]

Aluminum will oxidize but will generally stop with just an extremely thin coat that protects the metal beneath it. If an electrolytic reaction occurs the oxidation can be worse. This can easily happen if the aluminum comes in contact with another type of metal. My aluminum Nokon cable housing is pretty much rotting away because of this.

 

[The Toninator]

sweat does bad things to al ask wumpuss.

 

[golgiaparatus]

I was planning on repainting this frame matte black anyway... what If I were to sand the corosion away and spray it with primer?

 

[Reactor]

I was planning on repainting this frame matte black anyway... what If I were to sand the corosion away and spray it with primer?

No reason it wouldn't work. Aluminum oxide bonds to al very tightly and rapidly. I'd sand it, prep it and prime it as fast as reasonably possible.

 

[golgiaparatus]

No reason it wouldn't work. Aluminum oxide bonds to al very tightly and rapidly. I'd sand it, prep it and prime it as fast as reasonably possible.

Will it corrode through the AL like rust will with steel? Or is it more or less a surface thing? Does it tend to spread?

 

[T-Dog]

I had the same problem in the same spots with a used frame I bought....I stripped the old paint and sanded it good, then had it powdercoated (matte black). worked out fine.

 

[skatetokil]

it shouldnt affect the structure of the metal. under normal circumstances al oxide forms almost immediately after al is exposed to air, and if i remember correctly, its actually stronger than the unoxidized al. it sort of forms a hard case around the metal. the bubbly **** might just be contamination of some sort under the paint. who knows, but its nothing to worry about.

 

[V-Dub GTI]

i had that problem once. i just cleaned it up and used some clear coat over top of it to protect it.

 

[Reactor]

Will it corrode through the AL like rust will with steel? Or is it more or less a surface thing? Does it tend to spread?

no not really. The oxide layer is very strong, and doesn't spread like iron rust. However if you have two different metals making contact it can pit and spread slightly (galvanic corrosion). If you sand it and paint it, you won't have metal to metal contact and the corrosion will stop.

 

[urbaindk]

no not really. The oxide layer is very strong, and doesn't spread like iron rust. However if you have two different metals making contact it can pit and spread slightly (galvanic corrosion). If you sand it and paint it, you won't have metal to metal contact and the corrosion will stop.

What he said. Aluminum oxide is very stable an self-passivating so if you scratch it it just forms a new oxide layer. I suspect that you have some kind of mechanical rubbing that is constantly wearing away the oxide layer and thus building up wear debris (the white powder).

Also note that iron (steel) will oxidize aluminum so make sure you grease your threads.

 

[golgiaparatus]

What he said. Aluminum oxide is very stable an self-passivating so if you scratch it it just forms a new oxide layer. I suspect that you have some kind of mechanical rubbing that is constantly wearing away the oxide layer and thus building up wear debris (the white powder).

Also note that iron (steel) will oxidize aluminum so make sure you grease your threads.

Yeah I actually know the steel/aluminum thing. I've had a couple of steel fames with Aluminum posts that got pretty stuck.

The thing about the corrosion on this particular frame is that it was under the paint, no scratches, no exposed aluminum at all.

 

[T-Dog]

The thing about the corrosion on this particular frame is that it was under the paint, no scratches, no exposed aluminum at all.

On my older C-dale frame the bubbling seemed to start at the cable guides, which are mounted into little holes in the top tube. When I put the new guides on, I also put a dab of silicone sealant under them to seal the holes.

 

[urbaindk]

Yeah I actually know the steel/aluminum thing. I've had a couple of steel fames with Aluminum posts that got pretty stuck.

The thing about the corrosion on this particular frame is that it was under the paint, no scratches, no exposed aluminum at all.

You say it's at the fastener for one of the cable stops? Is it at a weld? Without seeing it, I'm guessing that there is some incompatibility with the cable stop, the weld, or the frame. Just for shiites and giggles, take a magnet to the cable stops and see it they are steel. If that is the case, it was poor materials spec from the manufacturer.

 

[johnbryanpeters]

Oh, c'mon. Ain't going to be steel welded to an Al frame. The white Al2O3's probably from a little galvanic corrosion from sweat plus steel cable plus Al frame. Sand off the oxide, do your general surface prep and paint or powder coat away!

Second thoughts:
It could be caused by a contaminant inclusion in the weld, but for a cable fitting that's no big deal.

 

[DirtyMike]

Clean it up as best you can with a small wire brush or something like that, touch it up with some Nail polish, normal to see on aluminum when there is a small hole in the paint, see it on Custom wheels all the time

 

[golgiaparatus]

You say it's at the fastener for one of the cable stops? Is it at a weld? Without seeing it, I'm guessing that there is some incompatibility with the cable stop, the weld, or the frame. Just for shiites and giggles, take a magnet to the cable stops and see it they are steel. If that is the case, it was poor materials spec from the manufacturer.

Actually they are not cable "stops" the are cable routing loops. They are plastic. The problem was caused because they are not welded to the frame... they are attached to tiny holes in the AL, how stupid. Anyway... removed all the plastic routers last night. JB welded the holes shut... sanded them smooth and spray painted the top tube with matte black primer. Looks totally ghetto, I love it. Cant wait to drop some roadies with their their team kits and their 5k carbon bikes on my spray painted bike with old Time ATAC Alium pedals, MTB shoes and my MTB helmet with visor.

 

[Jim Mac]

Thread Hijack: How do people feel about using raw frames? I am thinking of getting my R9 raw, but am afraid of the whole oxidization thing. I will check to see if it's clear coated, but somehow I don't think so...

 

[T-Dog]

My Prophet is raw, but does have a clearcoat and I like it. I had a problem with paint chips on my original cannondale HT, so I stripped all the paint, then polished it (by hand) and 10 years later it still looks good. No clearcoat, so I have to clean it every so often with Mothers or similar metal polish to really make it shine, but it's pretty low maintenance.

 

[Wumpus]

sweat does bad things to al ask wumpuss.

I have another bar that the end snapped off of that was a mix of sweat and a couple of wrecks and one last uphill grunt.

 

[urbaindk]

Oh, c'mon. Ain't going to be steel welded to an Al frame. The white Al2O3's probably from a little galvanic corrosion from sweat plus steel cable plus Al frame. Sand off the oxide, do your general surface prep and paint or powder coat away!

Second thoughts:
It could be caused by a contaminant inclusion in the weld, but for a cable fitting that's no big deal.

Yeah, I pretty much agree with you there.

 

[golgiaparatus]

I have another bar that the end snapped off of that was a mix of sweat and a couple of wrecks and one last uphill grunt.

Damn... what do you sweat bettery acid or something? My bars have never done that.

 

[urbaindk]

I have another bar that the end snapped off of that was a mix of sweat and a couple of wrecks and one last uphill grunt.

Lock-on grips with the hard plastic tube inside the grip,like an ODI or similar design. Am I right?

 

[Wumpus]

Lock-on grips with the hard plastic tube inside the grip,like an ODI or similar design. Am I right?

Nope bar ends. The sweat was getting sucked/syphoned under the grip where it met the barend. I have sinced solved the problem by running regular grips and no bar ends.

 

[Wumpus]

Damn... what do you sweat bettery acid or something? My bars have never done that.

It's the quantity not the quality, but you can also see the pitting on the brakes.

 

[golgiaparatus]

It's the quantity not the quality, but you can also see the pitting on the brakes.

I sewat like crazy and have never seen this on any of my bikes anywhere. You like salt dont you

 

[Wumpus]

I sewat like crazy and have never seen this on any of my bikes anywhere. You like salt dont you

You just think you sweat like crazy. I sweat close to three liter an hour in the summer.

 

[loco-gringo]

I sewat like crazy and have never seen this on any of my bikes anywhere. You like salt dont you

Honest to God. We were stopped one day, waiting on a dude to fix a flat or something, and someone asked Wumpus if he was pissing himself. It's really that much. Ugh.

 

[golgiaparatus]

You just think you sweat like crazy. I sweat close to three liter an hour in the summer.

I sweat 10 times more than most humans, people make comments if they are riding and dont know me... "did you just pour a water bottle over your head". I hate it... anyway, so I do sweat like mad... When I ride in the summer I am literally soaked from head to toe half way through the ride... even my gloves. Next summer I'll make sure I sweat into a bucket so I can measure it and compare to your 3 liters an hour we'll have a 'sweat off'.

 

[Wumpus]

Next summer I'll make sure I sweat into a bucket so I can measure it and compare to your 3 liters an hour we'll have a 'sweat off'.

 

[loco-gringo]

Do you sweat through your shoe cleats, golgi? There is no comparison to Wumpus' sweating. His title should be monsoon.

 

[golgiaparatus]

Do you sweat through your shoe cleats, golgi? There is no comparison to Wumpus' sweating. His title should be monsoon.

LOL! I've honestly never noticed or checked. I know once on a hike I sweated completely through my backpack ruining a bag of **** that I was planning to enjoy on the trip back

 

[DRB]

LOL! I've honestly never noticed or checked. I know once on a hike I sweated completely through my backpack ruining a bag of **** that I was planning to enjoy on the trip back

What were you carrying a bag of **** for?

 

[golgiaparatus]

What were you carrying a bag of **** for?

I like to have it just in case I need to burn it on someone's porch.

 

[loco-gringo]

I like to have it just in case I need to burn it on someone's porch.

I'm glad that's what you meant by "smoke" it.