Aluminum frame bubbling paint

[drexal77]

Hi guys, just picked a 1996 Cannondale frame. The paint is in 90% good shape. But there is sadly quite a bit of bubbling in certain areas on the frame.

Please see images attached.

I've tried to read up as much as poss before coming on here about the best thing to do with this, but only really managed to find reddit forums. So thought i would ask on here as i know some of you guys are absolute gurus.

I've read that you should rub down all the bubbling paint and remove the aluminum oxide and then either primer these areas or polish them.

And i did find this post:

https://www.retrobike.co.uk/threads/bubbling-paint-on-carbon-and-alu.481773/
Would you agree this is best course of action?

I removed the paint from the worst effected part of the frame on the rear stay. And found quite a deep hole it not sure if this is pitting from corrosion or if it got punctured and that's what caused the corrosion the hole doesn't go right through to the inside of the stay. But is prob at least 2mm deep. Would you be worried about this and if effecting the structure of the frame?

Finally is there anything you can fill this hole in with to try and bring back the strength?

Thanks to anyone that replies.

 

[d8mok]

Well known issue on Cannondale frames.

That frame is toast unfortunately looking at the pics.

They go soft and you can sometimes even push your finger through them.

 

[highlandsflyer]

Find some imaginative use for it, but don't put it back on the road.

 

[bikeworkshop]

This looks like one of these cannondales that was retired to the turbotrainer,
where the owner drips sweat onto it for a couple of years.

Never needs cleaning cos it's never dirty.

The salt sweat gets under the paint edges just like this one, and can cause enough corrosion to eat right through the tubes

 

[drexal77]

Hi guys thanks for quick reply by you all. Yes I read a whole forum about trainer bikes & how bad sweat can be. Absolutely gutted been after this particular bike for so long it’s a 1996 m900.

So you don’t even think it’s worth sanding off all the corrosion (there is literally only about 4 tiny places where its bubbling & polishing them up to see if any corrosion comes back. Or do you think even if no new corrosion comes back that the structural integrity of frame / aluminum is now compromised?

Even in the corroded areas, the metal doesn't feel soft that you can push it in with your hands.

Would none of you even use the bike for riding on the roads & canal paths (so no jumps or drops) around London at w-ends?

So gutted its a beautiful frame with how clean the shape is and the beautiful curved welds, feels such a waste to go on the wall. I was also thinking of trying to buy a 93 m800 but its now put me off cannondale's and going for an even older bike after this. Thanks so much for all your honesty and advice. So sad, what a waste of a bike

 

[ishaw]

Blimey. I'm worried what I might find under the bubbling paint on my trek now.

 

[d8mok]

Blimey. I'm worried what I might find under the bubbling paint on my trek now.

Cannondales are prone to it. I’ve had more with the issue than without. They just seem to rot badly compared to other stuff of the same era and material.

 

[bikeworkshop]

Would none of you even use the bike for riding on the roads & canal paths (so no jumps or drops) around London at w-ends?

To be fair to cannondale, the frame has lasted well. They chose the alloy for its light weight and stiffness - corrosion resistance was further down the list, say 10 years of sweat?
Paints of that period didn't stick brilliantly to alloy either, allowing moisture to penetrate at the edges.

you could clean it back, touch it back in and use it, just inspect those damaged areas regularly. Cracks usually propagate over several rides.

Given the damage is corrosion not stress, it's no worse than loads of other retro bikes, with chainstay horrors lurking under the paint, or rotting from the inside out.

Nothing lasts for ever.
You just don't want to be descending a mountain road at the end

 

[7Speed]

Like the guys have said - I would let this one go. It might bite back without warning no matter how much love you throw at it.

 

[ishaw]

I'm all for safety and agree it's probably not going to take a lot of punishment but you could try something like J-B Weld:

https://www.jbweld.com/?srsltid=AfmBOoqwghxrTfIKUQqOJTwL5d4X4zKpTWebyRxt9jb7h4KY2G0e0N08