I got my old winter road bike out last night and found that the paint had delaminated in isolated places to the point that you could just pick it off. Under the paint the aluminium (Scandium) had what appeared to be a chalky residue on top of it.

The bike is about 12 years old. Can anyone explain what’s happening and if it’s safe to carry on riding.

thanks

No expert but sounds like oxidisation

Yep, that’s corrosion. It’s fine to ride.

corrosion. no probs to ride.

As above, it’s fine, unlike steel which oxidises, increases in volume and loses all it’s strength and hardness (aka rust flakes). When aluminium oxidises it forms an even harder surface which stops it getting any worse which is why aluminium components are often bare. The downside is the paint still bubbles/flakes off it as the surface breaks up.

If it’s still within warranty you could try that route, otherwise I’d ignore it. The headtube of my road bike’s been doing it where the headset fits and water gets in under the cup. 3-4 years, not dead yet.

it would only concern me if it was at an area where it was bonded to carbon.

ie forks or rear stays…..

This sort of corrosion is hugely worsened by having and electrolytic solution between two dissimilar metals, which is why is a really good idea to keep road bikes washed from road salt.

great thanks all.

mind a rest.

Yep – as above – had this on an older frame some years ago in a few spots – give it a really good clean, lose any flaky bits and then keep it nicely waxed. This should keep it at bay.

Also caused by undiluted Muc Off…