Aluminum frame bubbling paint

[retrobate]

Remove the oxide with abrasives (wear a mask) & assess how much the tube wall thickness has been reduced, if you think it is significant bin the frame if not do the follwing.
Open up the hole with a drill to remove stress raisers to reduce the risk of cracking.
Treat the bare metal with Alocrom 1200 (or whatever the modern equivelent is).
Fill the hole & any pitting with Devcon or JB weld.
Etch prime & then paint.
Ride and enjoy until it cracks somwhere else, it is a Cannondale 30 year old aluminium alloy frame after all

 

[d8mok]

Or option B - buy a replacement frame for less than the cost of the bits needed to make this right.

Last solid m600 frame I sold went for sub £20. Just buy a good one and bin this.

 

[Twozaskars]

Please cut it two and just get rid of it, stop someone hurting themselves.

 

[retrobate]

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.

Would you agree this is best course of action?

If a m900 is what you want the options are
Best option

Or option B - buy a replacement frame for less than the cost of the bits needed to make this right. And inspect the frame regularly for cracking

2nd best option

Remove the oxide with abrasives
Open up the hole with a drill to remove stress raisers to reduce the risk of cracking (if not a hole blend out pitting).
Treat the bare metal with Alocrom 1200.
Fill the hole & any pitting with Devcon.
Etch prime & then paint. And inspect the frame regularly for cracking

3rd best option

Remove the oxide with abrasives
Open up the hole with a drill to remove stress raisers to reduce the risk of cracking (if not a hole blend out pitting).
Prime & then paint. And inspect the frame regularly for cracking

4th best option
Just ride it, And inspect the frame regularly for cracking

Please cut it two and just get rid of it, stop someone hurting themselves.

Options 2 & 3 do require some engineering judgement but lets not get carried away, aluminium oxide has a volume far greater than the parent metal it came from (I dont recall the exact figure but 9-10 times rings a bell - dont quote me though) so its possibly not as bad as it looks. The good thing is that the corrosion is on the outside so at least you can see what you are dealing with.
At the end of the day Its a 30 year old ally frame, it and any aluminium frame will fail due to fatigue at some (undetermined) point, maybe not in your lifetime but eventually.
The greater risk is more likely to be 30 year old lightweight aluminium handlebars

ps Inspect regularly for cracking

 

[greencat]

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?

I used to regularly commute in London, and the state of the roads definitely contributed to one of my frames cracking.

 

[Twozaskars]

If you’re going to rub it down (in fact, I think you owe it to the world now - in the interests of science and safety or whatever) you should not use your usual steel wire brush, use a brass or even better a poly wheel in your drill like the example below. That way, if you do repaint it and put it back into service there will be no traces of iron left embedded into the aluminium to start any galvanic corrosion.
https://www.ebay.co.uk/itm/39529372...6iRXLTORNu&var=&widget_ver=artemis&media=COPY

 

[retrobate]

If you’re going to rub it down (in fact, I think you owe it to the world now - in the interests of science and safety or whatever) you should not use your usual steel wire brush, use a brass or even better a poly wheel in your drill like the example below. That way, if you do repaint it and put it back into service there will be no traces of iron left embedded into the aluminium to start any galvanic corrosion.
https://www.ebay.co.uk/itm/39529372...6iRXLTORNu&var=&widget_ver=artemis&media=COPY

Good point. I like these

https://www.cromwell.co.uk/shop/abr...MIv5XRv8_TiAMVtJhQBh3XAhcZEAQYASABEgK4DvD_BwE
but wet & dry paper would be fine.

 

[drexal77]

Hi all,

Sorry for only replying now. I saw some of your replies coming in, but had the kids all w-end, so just could not get enough time to reply. Thanks for everyone's input, this site is by far the best on the internet. Really interesting replies. And thanks for advice from the people with safety concerns. That's crazy that @d8mok your frame only sold for £20 and i know you said to just get another frame. But trying to find the exact year that the right price and in the correct size for me is pretty much impossible and some times take years of waiting for one to pop up. After more exploration work i will make the call if it looks to bad. I will then retire to it to be wall mounted. And thanks for advice @bikeworkshop & @retrobate on a possible way to save / prolong it. And for advice and posting the sanding discs @Twozaskars.

As i have some sand paper and some wet & dry in the cupboard i'll tackle this stay area as it looks the worst first and take a look at that hole in more detail, but i'll order these for the other areas. And i have some JB weld already so i'll have a go at that to. I sadly don't have any parts free to chuck on this bike so i can just try going for a very slow controlled ride to see what happens now these areas are exposed. But i promise to keep you posted with how the rest of the frame looks under the other bubbled areas. Also @retrobate thanks for advice on Alocrom 1200 i had never heard of that. But did a load of research on it in bed last night. That is a pretty extreme product, it says you should bottle it after use and take it to a specialsed tip to dispose of it. And looks like its been banned now in the Uk. But like you said i will look for a modern equivilent. But it looks like these products are aseome and can help to prelong the aluminum for years to come & allow for paint to stick to frame properly. Thanks again will keep you in the loop with my finding.

 

[Antwack]

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