Carbon Fibre/Aluminium Corrosion

[pablo180]

Hi i have a LOOK KG241 which has carbon fibre tubes and aluminium lugs. Bought it used recently and have realised there is some corrosion between the carbon fibre tubes of the frame and the lugs making the paint bubble. Also on one of the joints (headtube+frame) there is a tiny visible gap between the frame and the lug. How serious is this/how quickly does it corrode? How can i fix it?

Thanks (sorry if this is in the wrong place)

 

[youngoldbloke]

I noticed possibly similar bubbling and subsequent flaking of the paint finish on carbon fibre forks in the area where the fibre fork blades joined the alloy fork crown and steerer assembly. There was similar bubbling around the alloy drop-out/blade junction. I removed the finish to expose the join between the alloy and fibre, and discovered that corrosion of the alloy surface was causing the bubbling of the finish. There was no apparent structural weakness, or separation of the fibre from the alloy. However, this was on a 'hand me down' bike, which I knew had had heavy commuting use, and although I used the bike with the original forks for a number of months I eventually replaced them. I suspect the corrosion was due to water ingress, but in this case could not rule out the possibility of accident damage as I didn't know the bikes detailed history.

 

[Globalti]

Unprotected alloy does corrode and the corrosion can spread in little tracks under the lacquer. If moisture is penetrating the tube to lug joint there will be corrosion but I bet it will be a few years before this becomes bad enough to compromise strength.