There's a late 90s Trek 5200 for sale locally. The current owner used automative paint to cover the original paint job, which is chipping away and revealing whats underneath. Can I sand the frame down, removing both the automative paint and the original paint, before painting it myself? My ideal end is to have a single color design, something nondescript. Perhaps removing the original is not necessary, but maybe unavoidable if the automative paint is to be removed too.

I think there used to be a paint stripper called "Carbolift", with mixed reviews. But I tried to get some a few years ago and struck out. Now the company seems to be defunct.

Here is the MSDS, but it is very uninformative.
https://powder365.com/wp-content/upl...olift_MSDS.pdf

It does seem to have some hydrogen peroxide in it.

Anyway, if you're not wanting to preserve the paint, I'd probably go with sanding. If you were lucky, there would be a heavy clearcoat over the factory paint, and you could gently sand through the top coat into the clearcoat without destroying the factory paint.

However, 20 years old, it is quite possible it was repainted because the original paint was damaged.

Could poor original paint be causing adhesion issues with the new paint?

If you come up with a wonder treatment, I picked up a vintage Giant CADEX road bike frame at the local bike coop that had been poorly painted. It could be practiced on.

I would also want to ask the seller why the frame was repainted. Could just be a 25 year old frame started to look a little ratty from normal use or there was damage that was covered up.

The makers of the bike probably primed and painted it with the ideal stuff at the ideal moment in the ideal conditions. Why would you want to take that off and chance that you know what the correct primer or paint is to bond to that frame material? As much will you have the ideal conditions?

I'd just sand down what ever paint is loose and feather back to good adhering paint any chipped or flaking edges. At most I might sand till I remove any finish that isn't original.

Sanding really doesn't take long on a bicycle once you get going.

This, plus maybe a little sanding to make sure whatever paint is left isn't super smooth/glossy. Maybe I'm wrong (probably am), but an even surface (but slightly rough) seems like it'd allow paint to adhere better than whatever clear is on top.

I took to the forums to seek the expertise of others with which I might better inform myself what it is I ought to do. What I want is to have a bike that isn't the color of the original, an electric blue, nor one that has a rough exterior as it does now. You've set me right in explaining that I wouldn't want to remove the original paint coating and your idea of keeping all but the poorly adhering paint sounds like a good one. Once I've done this, would you advise priming, then color-coating and clear-coating? Thanks for giving your take.

IMO, you don't have to prime all the time. I usually will on something that I want to look good. If nothing else it gives a chance to see where surface imperfections are that might need some more attention. Those sometimes are not so easy to fix if you just spray the color coat. High build sandable primers are great for this if the paint you are spraying on them is compatible.

I'd clear coat anything that I wanted to protect the color coat from getting scratched to the primer. Easier to fix a scratch in the clear than a scratch in the color...... usually. As in everything, it depends on what paint and primers you use. And how bad you want to make it perfect.

Thanks for the response. How would you address surface imperfections revealed by the primer? This would be my first time preparing and painting a bike, so it's my assumption (which may be incorrect) that the goal of primer coat is to create a uniform surface and one to which the color coat can adhere well. To achieve surface uniformity during the priming phase is it as simple as applying primer and sanding in between coats to remove imperfections? Thanks for your help.

"Bondo Glazing and Spot Putty" will likely fill in the scratches/imperfections more quickly than reapplying more layers of primer. But I've only ever painted cars, and not bike components, yet.

I’d prep with 400-600 grit.

As for the finish, do a light layer and once dry, sand it smooth with about 1200-1500 grit. I do it wet with clean water. Be sure to clean the frame with denatured alcohol between layers. I think about 3-4 layers is best.

Once you’ve got the layers on, do a final wet sand with 2000 or even 2500 grit, with polishing compound. Nice and wet.

Personally, I wouldn’t mess with clear coat at all. I’ve seen it react to fresh paint (even a couple days old) and ruin the whole thing.