View Full Version : Rotary polishing on Carbor Fiber?

Mar 9th, 2006, 08:02 PM
Hello all,

A friend of mine recently purchased a painted carbon fiber trunk lid for his Lancer Evo. Well whoever painted the trunk did a pretty poor job of it so he had to wet-sand the whole thing to take down the little "bubbles" that formed in the clear coat. Anyway, he doesn't have a PC or a rotary so he asked me if I could help him out with removing the remainder of the fine scratch marks left over from using ScratchX.
Since PC is not quite the right tool for the job, are there any concerns with using the rotary with maybe a #8006/#80 combo on the carbon fiber material? My friend is currently trying to get the painter to repaint, as well as add more coats of clear coat (my friend was able to sand right through to the carbon fiber after a few light strokes). So what do you guys think? Thank you.


Mike Phillips
Mar 10th, 2006, 04:55 AM
It's been interesting the increase in people on forums attempting to wet sand without understanding all the ramifications. What I always post is, it's easy to wet-sand, it's getting the sanding marks out that requires a little skill, knowledge and experience.

There are two kinds of carbon fiber components, coated and uncoated. I've been told they cannot include a UV inhibitor in polyester and epoxy resins, thus uncoated carbon fiber components are vulnerable to fading and deterioration. To add UV protection to a carbon fiber component, they are sprayed with a clear coat of paint like a clear coat finish on a car and this clear coat finish has UV inhibitors in it.

The question is, did your friend sand through a clear coat layer of paint, or through the resin coating into the fibers themselves?

Either way, it's time to stop. Back away from the trunk lid. Find out what you're working on and then hopefully from the manufacture, and then find a qualified painter to try to salvage the component by prepping it correctly to re-paint.

Good luck.

Mar 10th, 2006, 06:27 AM
Thanks Mike for your reply...

I have read many times on this forum about the possible consequences of improper wet-sanding and what it will take to fix, and believe me, I tried to dissuade him from doing it. It is hard enough wet-sanding metal surfaces, but to do it on a material such as carbon fiber that is unknown to many... In the end, he paid for the trunk, it is his property, so he made the executive decision.

The trunk is painted and has a clear coat, but neither him or myself know whether it is coated CF or uncoated. I told him to stop working on it that same day when we started to see exposed CF (the typical blackish weave pattern) on the edges, and now he is waiting on the painter to take it back and repair.

One thing is for sure, you won't catch me putting anything that has grit on paper-backing to my car... :-)

Thanks Mike! I'll go smack my friend now... :-)

Mike Phillips
Mar 10th, 2006, 06:37 AM
Originally posted by pklin

I'll go smack my friend now... :-)

With a clean, soft, plush Supreme Shine Microfiber! :laughing

Mar 10th, 2006, 06:43 AM
Nah... That'd be too easy on him...

I was thinking of trying my new Meguiar's Super Suede drying towel... Loaded with water... :D

He'll be attending one of your Detailing 101 classes in May... I'll be sure to have him identify himself to you as the "Carbon Fiber Sander" so you can smack him again... But this time with the MF. :D Be sure to load him up with goodies afterwards so he doesn't cry too much.

Mar 21st, 2006, 12:55 PM
probably 95% chance that the trunk has an exterior clear coat, as people usually buy the trunks for their look - and hence manufacturers put the clear on them so they look nice.

what is your friend trying to get out of this? does he want the CF look, or a painted trunk - in which case he should have just stuck with the stock lid, as its plenty light already (i drive an evo too :xyxthumbs )

to answer your question, the trunk very likely has a clear coat on it, you can use a rotary on it, as the clear coats are quite durable since they are normally used as the exterior protectant. (look at the horizontal part of his stock wing, assuming he has it, that clear that is protecting the CF weave on the wing is what the trunk most likely has on it)

this probably wont happen, but if you ever are using a rotary or sandpaper (like to strip the paint or something, i dunno) and you see black on the pad or paper. stop. those are the actual fibers that you are sanding into. of course assuming it was not painted black in the first place.

if you know or can find the manufacturer, you'll be able to search on google and easily find whether it has a clear coat or not