Carbon frame corrosion

[alex4478]

Hi,

Apologies for this being my second post here, but I have noticed some corrosion on the seat stays of my bike.

Is this something to be worried about?



And ...

 

[PhilDawson8270]

Looks like carbon frame with aluminium drop outs, quite common.

Though they do look more like impact damage.

 

[gbb]

Rub down the minimum required to get rid of the corrosion, inspect for cracks etc then paint over and lacquer if you feel the need. Similar happened on my Bianchi at the junctions of carbon forks and the alloy steerer. Once cleaned and painted,it wasn't an issue.
Someone may have a product that kills alloy corrosion..I didn't bother.

 

[raleighnut]

Did you take it out in the rain?

 

[vickster]

Did you take it out in the rain?

Maybe the rest of the bike melted and that's all that's left

 

[boydj]

I agree with Phil - that does not look like corrosion - more like something has taken a gouge out of the frame.

 

[Citius]

No, its corrosion, 100%. The aluminium end on the stay has begun to oxidise and the paint has lifted and then flaked off. The only worry is that is an ally end bonded into a carbon seat stay - if the corrosion begins to extend into the bonded area, there could be a problem.

 

[gbb]

No, its corrosion, 100%. The aluminium end on the stay has begun to oxidise and the paint has lifted and then flaked off. The only worry is that is an ally end bonded into a carbon seat stay - if the corrosion begins to extend into the bonded area, there could be a problem.

Agree 100%. Alloy doesnt rust but It does turn furry white when it oxidises and soon blisters up any paint on it.
An inspection of an alloy frame every now and again should be routine, look for chipped paint, clean and at least protect with a dob of nail varnish to stop further corrosion. Obviously OPs bike is carbon, but alloy needs care to prevent corrosion.

 

[screenman]

I would always use an etching primer when painting alloy. Before applying base coat and laquer.

 

[alex4478]

Thanks for the comments.
So the conclusion is that it is corrosion, the aluminium has oxidised and began to degrade. The issue is that the corrosion could travel up and "lift" the carbon away from the alu bonding.
To combat this I could sand down the corroded part, treat with an etching primer (what is that?), touch up with some paint (I was thinking PlastiKote) and then use some lacquer (Nail varnish, or PlastiKote).

The obvious question that I haven't asked is ... Is the frame fubar'd?

 

[PhilDawson8270]

Aluminium oxidises within seconds of being exposed to the air. It is oxidation layer that protects our from corrosion and what makes it so good for anti corrosion.

It weighs need to be exposed for a long time to go furry like it does.

Op long did it range for this to occur? I can see scratches right above the bar aluminium on the dropouts, has paint been missing here a while?

 

[Globalti]

That's a rather neglected Roubaix of about 2006 vintage, I had the same on mine. Moisture gets under the very thick hard paint and travels around before the paint breaks away. Clean it all thoroughly, remove paint, etch prime (this is a paint that eats into the surface of the alloy to get a good key) and hope the moisture hasn't wicked up between the dropout and the tube. While you're at it, check the alloy bottle cage bosses - mine oxidised under the drenching with water and carbs mix and fell out. Repaint everything then cover in lacquer. A good repair might get you a few more years out of the frame.

 

[alex4478]

That's a rather neglected Roubaix of about 2006 vintage, I had the same on mine. Moisture gets under the very thick hard paint and travels around before the paint breaks away. Clean it all thoroughly, remove paint, etch prime (this is a paint that eats into the surface of the alloy to get a good key) and hope the moisture hasn't wicked up between the dropout and the tube. While you're at it, check the alloy bottle cage bosses - mine oxidised under the drenching with water and carbs mix and fell out. Repaint everything then cover in lacquer. A good repair might get you a few more years out of the frame.

It does look neglected, the wrapping around the tubes is from some electrical tape that was used to 'protect' the frame from a mudguard that had been fitted using ruber bands.

I'm really wanting to restore this frame, what would be the best way to remove light scratches, dings from stone chips and the like?

 

[Globalti]

Strip it completely, rub it down with wet and dry, fill any remaining blemishes with plastic padding, rub smooth, paint, lacquer. A professional re-finish by someone like Atlantic Boulevard in Bury would cost something like £200 but restore the frame to new.

A cheaper DIY option would be to flat the paint gently with fine wet and dry then simply re-lacquer.

Is the corrosion on the dropouts deep enough to be weakening the joints with the tubes? Are there any witness cracks elsewhere in the paint?

 

[Mobytek]

corrosion will expand the part inside the carbon and eventually it'll butst and delaminate.

Point is how did the outer laquer get damaged to allow it to corrode - probs a hit / crach / impact.