The clear coat on my 2 year old Campy SR front derailleur cage has inexplicably begun to peel off. This bike was never crashed, and there was never any episode where it was scraped against anything that I can recall. My bike shop suggested that I just repair it with clear nail polish, but since there was no trauma, I am wondering if anyone thinks this is a warranty issue and that I should press for a replacement cage.

It's only cosmetic, sand it and put some clearcoat on it.

Mech exactly looks like the numerous records versions I saw where the owner changed to a bigger ring / from compact to normal and forgot to adjust the height. Looks exactly like the damage caused by the tooth scraping the carbon.....

At least yours lasted 2 years...Same thing happened to mine after like 2 or 3 rides. Could take a photo after work. Really annoying. In retrospect, I would opt for a no carbon cage every time. Even though it still functions fine, its not worth the 3 or so grams that you save over a Chorus f/d.

I've read about this happening to others. As far as I know, no warranty. It is a bad place for carbon IMO. Perhaps it is the tooth scraping, I don't know. All I know is that my derailleur height was setup exactly in line with the sticker that came on it.

I would be interested to know how the nail polish works, or anyone else has any other methods to fix this.

Look on the bright side. This is WW, and with the loss of clear coat, you've saved a fraction of a gram.

i think it happens when the fd is set a bit high. then when the fd pushes the chain from the large ring to the small, the chain drags on the underside of the outer cage plate. since it's the top edges of the chain plates pushing sideways, it's a lot like a chisel edge scraping the clearcoat.
i am not certain this is the case, but i have seen a few derailleurs that have experienced this phenomenon.

I know for a fact, mine was the result of the derailleur sliding down the seat post. I have a Parlee carbon clamp and it took some time before I found the right type of shim to add to keep it from sliding down [cloth tape was the ultimate shim, right traction and thickness].

Not saying you have the same problem but after looking at your photo again, there is some clear coat on one of the teeth and the scraping on the carbon cage is exactly like mine [full length scraping along the entire bottom cage].

That is a pretty common front derailleur malady. Fortunately, it is only cosmetic. Be thankful don't have Di2, where the peeling chrome looks much worse...

Thanks everyone- I put some clear nail polish on it last night and a second coat this morning before heading to work. I'll let you know how it works. (by the way Butcher, that's not a flake of clear coat on the chain wheel tooth, its a bit of paper towel- I rode through a puddle and gave the bike a quick wipe down when getting to work!). Thisisatest's explanation is intriguing, although as best I can tell the derailleur height has always been spot on, but I did need to adjust the travel last season as upshifts were not quite right.