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Paint decay

Old 02-21-22, 11:09 AM
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CrowSeph
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Paint decay

During the first ever quarantine (mar-2020) a started a project and then i left in the dust since the parts missing were a lots.
The bike has been repainted with spray cans (metal primer , color and trasparent).
i remember that the paint was stiin in good shape even after some months.

Now after years i took a look into that old frame and surpicing i saw the paint in this conditions.
what cause paint to became like that?


(no water or even the sun has been touched directly the frame during the time it was in stand-by).
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Old 02-21-22, 02:25 PM
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Oh, d' Italia... That must be the problem.

My old Colnago Super did the same thing. It likely had a factory repaint years before I got it. And, the paint was probably pretty good for 30 years or so, then it just went bad... very bad.

I think the paint crazing must have happened during my time in Missouri, with two factors. The possibility of road salt exposure, and some extreme heat (or heat/cold cycles).

A few things you might look at. Incompatible paints for various layers. Was there any painting over paint?

Bad surface prep. Clean, dry rust free bare metal.

Too thick of paint layers.



I thought the instructions was to always wait until 90% dry, then recoat. But, if too thick, apparently it is recommended to let it completely dry, then scuff before the next coat.
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Old 02-21-22, 03:12 PM
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Originally Posted by CliffordK
Incompatible paints for various layers. Was there any painting over paint?

Bad surface prep. Clean, dry rust free bare metal.

Too thick of paint layers.

I thought the instructions was to always wait until 90% dry, then recoat. But, if too thick, apparently it is recommended to let it completely dry, then scuff before the next coat.
Hello! The paint has been completely removed and the frame was prepared almost with perfection (no rust , no contaminants). Primer , the paint and the clear coat were the same brand (so i exclude the possibility of incompatible paint either)
Once i experienced the same problem when a frame a frame was contaminated , but that effect appears after a couple of hours after the praint. That's is so strange because we are talking about years and not hours.
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Old 02-22-22, 08:08 AM
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One of my other hobbies is playing guitar. Many (most) guitars that have a nitrocellulose finish, or nitrocellulose in the paint, have a similar look as your paint, as they age. Any nitrocellulose in the paint you used?
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Old 02-22-22, 08:23 AM
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Originally Posted by CrowSeph
The bike has been repainted with spray cans (metal primer , color and trasparent).
This is the problem with all spray cans.

Spray cans have always been quick cosmetic fixes and don't provide long term results, more evident with DIY on their cars.

One of the reasons is the spray can dispersant chemical that is mixed with the paint, and this makes the paint very thin.

If you love a bike enough to give it a repaint, send it out for sandblasting and shop paint. Lots of vids like this on Yt.
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Old 02-22-22, 08:46 AM
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Originally Posted by soyabean
This is the problem with all spray cans.

Spray cans have always been quick cosmetic fixes and don't provide long term results, more evident with DIY on their cars.

One of the reasons is the spray can dispersant chemical that is mixed with the paint, and this makes the paint very thin.

If you love a bike enough to give it a repaint, send it out for sandblasting and shop paint. Lots of vids like this on Yt.
i used spray cans on lots of little project but this is the first time the paint decaded like this....
ps. I already have a sandblaster and two paint guns but for that bike seems to be time wasted
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Old 02-22-22, 08:47 AM
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Originally Posted by freeranger
One of my other hobbies is playing guitar. Many (most) guitars that have a nitrocellulose finish, or nitrocellulose in the paint, have a similar look as your paint, as they age. Any nitrocellulose in the paint you used?
Negative , paint was acrylic
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Old 02-22-22, 09:56 AM
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Acrylic, Urethane or whatever, doesn't mean anything as there are so many formulations of them. Some good, some not so good.
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Old 02-22-22, 10:16 AM
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It is very easy to get crackling on the second coat, or subsequent coatings from thereon if you do not wait for your paint to dry. If you wait too short of a time, what you’ll end up with is wet paint on top of wet paint. This means the paint below the surface is not subject to the same cooling qualities as the paint above, i.e. the external air, which means it won’t dry properly. However, the paint on top is drying perfectly fine, and will do shortly. Overtime, the wet paint beneath the surface will move as it sets, and will crackle the surface.
https://www.hellopractical.com/why-d...paint-crackle/

...I don't know what you were using, but it's not uncommon to run into something like this when mixing lacquer paints with enamel paints (even if they are made by the same company.) In your case, I would suspect that the color coat was an enamel, and the clear was a lacquer. But if you read the link, you'll see there are a great many ways that a paint job can crackle all over like that. Sometimes, it's done intentionally.
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Old 02-22-22, 10:21 AM
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Originally Posted by CrowSeph
Negative , paint was acrylic
...acrylic paints come in all sorts of formulations. Spray acrylic paints are a relatively recent innovation.
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Old 02-22-22, 10:38 AM
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Originally Posted by 3alarmer
https://www.hellopractical.com/why-d...paint-crackle/

...I don't know what you were using, but it's not uncommon to run into something like this when mixing lacquer paints with enamel paints (even if they are made by the same company.) In your case, I would suspect that the color coat was an enamel, and the clear was a lacquer. But if you read the link, you'll see there are a great many ways that a paint job can crackle all over like that. Sometimes, it's done intentionally.
interesting , tnx
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Old 02-22-22, 04:56 PM
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OP,
A number of things come to mind when looking at the paint on you frame.
Either the paints that you were using were not compatible with one another, even if they were from the same manufacturer. etc.
Another reason may have to do with the surface preparation itself any contaminants can cause this to happen BUT I suspect that the cotes before the clear was applied may have caused the crazing causing the topcoat to crack and craze that along with storage temps. etc.
I have used rattle cans in the past and they all do not have these issues...certainly not as strong as a baked on factory finish, but if a catalyst top coat is used they can and do provide good results....Been there done that.
Personally I like the "patina", it gives it a bit of character.
Best, Ben
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