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polishing scratched anodized crank arm(10 posts)

polishing scratched anodized crank armeflayer
Feb 24, 2003 6:47 PM
My chain derailed (twice) on the outside of my Dura Ace flawless crank arm. You might have guessed that it scratched the anodized arm and spider and marred the mirror finish. Not deep scratches, but visible. Is there a way to buff out the scratches without ruining the rest of the anodizing? I tried a bit of McGuires number 2 swirl remover but that didn't do much.
You can't buff out those scratches...davet
Feb 24, 2003 8:27 PM
...without going thru the clearcoat and anodizing. You'll just have to buy a new crankset!
what if the scratches are just in the clear and not deep?eflayer
Feb 24, 2003 9:03 PM
for instance on a car, light scratches in the clear can be buffed out with rubbing compound. Won't that work on the clear on the cranks?
The first thing...............davet
Feb 24, 2003 9:39 PM
If you threw your chain twice, the first thing is to adjust the high limit screw on your front dérailleur.

A dime will get you a dollar that the scratches are deeper than the clear-coat. But you could try a very mild rubbing compound, gently, too see if it will work. Unlike a car with clear-coat, there is no color on the crankset to hide the buffed clear-coat. On the crankset it protects the underlying aluminum, which will start to corrode on the surface with out its' clear-coat protection. Really, you should buy a whole new groupset! That's the only way to remedy the situation.
Nope, there's no clearcoat on the cranks.jw25
Feb 25, 2003 7:29 AM
What there is is clear anodizing, which is a layer of aluminum oxide built up through a special electrolytic bath. It prevents hazing and oxidation, since there's a layer of oxide already there.
Chances are good the scratches went through the clear anodized layer. If you buff them out, you'll remove a lot more, and end up with hazy components, which will require a lot more maintenance to keep shiny. There's very little danger from this oxidation, as it doesn't progress deep into the aluminum, unlike ferrous rusting, but it does look unsightly.
I'm afraid the best course of action is doing nothing. Heck, now your parts look ridden, kind of like new wheels after the first rain ride. Be proud of those scratches.
Nice philosphical approacheflayer
Feb 25, 2003 8:23 AM
I am taking your philosophical approach. The scratches are not that bad and now I finally learned how to adjust the f---ing front derailleur. No more derails, no more scratches. It's funny, on my other bike, I used purple degreaser on the chain and screwed up the anodizing on my Ultegra triple crank. They are machines, not pets. Right?
right - don't do it!DougSloan
Feb 25, 2003 10:57 AM
I tried this. I found out that it is not clearcoat, but anodizing. If you start buffing, you will get a spot that at first is highly polished, then hazes over. Neither the newly or older polished parts will match the existing anodizing, so the whole thing looks like crap. Just leave it alone, or you'll make it worse. That is, unless you want to polish the whole darn crank, which will take about a week getting all the anodizing off. Then it will look like crap anyway in a few months.

re: polishing scratched anodized crank armParticleMan
Feb 24, 2003 9:24 PM
u might wanan try an auto shop...what they use for buffing out and polishing such scratches on carparts...the dura ace logos may come off, but u get a polished crankset. better than getting new cranks!
re: polishing scratched anodized crank armNEIL
Feb 25, 2003 6:21 AM
They'll look great and better than new for a couple of weeks, until they start to turn this hazy gray color from oxidation. Then you'll have to do the process over again. I buffed up an old DA seatpost with a grinder and buffer wheel enough to take the clear coat off, and have to touch it up with steel wool every few weeks. I wouldn't do that again.
Meguiar's Scratch Xmghwk
Feb 25, 2003 6:05 PM
What about Meguiar's Scratch X? I used it on an older DA crankarm with good success. It is not a polish, but rather a filler. It fills in and rounds the corners of the scratch, making it almost invisible. Another option to see if this will work on your particular scratch is to use a carnuba car wax. This will provide a similar effect, but will not be as permanent. If it minimizes the appearance, you may be happy. The Meguiar's product worked well for me, anyway.