There is a “varnish” like coating on the Shimano cranks, does this pose a perpose. I have a crank set that has scratches but only appears to be “varnish” deep. If I remove this, what is the problem? Anyone know of a good method - green pad etc?
If you remove the coating, they will oxidize, meaning that the aluminum will turn dull grey (the color of corroded aluminum) and will be susceptible to stains.
It will not affect performance, unless you plan on using them a LONG time or live near the ocean, where you may actually may be able to see them corrode away…)
Campy cranks, and all other decent aluminum cranks AFAIK, all have this.
The purpose of the varnish is to scratch within the first mile of riding so that otherwise perfectly good cranks that sell new for $300 are practically worthless on the used market.
here’s something that you might do - clean the crank of the “varnish” (not really varnish - by the way). to clean it off you will have to use steel wool and / or very fine (600 grit or so ) wet /dry sandpaper with water and/or a buffing wheel with buffing compound. do this until the crank is scratch free and shinny as brand new. this could be a lot of work - so maybe just do one part of the crank assembly at a time - only where necessary. then spray paint the cleaned off part with a GOOD clear automotive type paint (something that say “plastic…” or " poly…" - not varnish and not lacquer - clear, strong, and hard. Then it will be like new — - – - until you scratch it again.
If you remove the coating, they will oxidize, meaning that the aluminum will turn dull grey (the color of corroded aluminum) and will be susceptible to stains.
It will not affect performance, unless you plan on using them a LONG time or live near the ocean, where you may actually may be able to see them corrode away…)
They’ll be like Ultegra SL’s…
Thanks for everyones feedback. I think oxidization may take a while, but was also thinking that instead of “painting” with poly-laquor, I could polish with somehting like TurtleWax - or some similar protectant?!!?
I removed the clear coat on a Ultegra 9-Speed group and polished it to a mirror shine. Yeah, it’s much more susceptible to scratching and oxidation. The cranks get shoe scratches much easier now. On the other hand, it is really shiny, 
and it’s not hard to get out some Mother’s aluminum polish and clean it up every now and then. I used plain old acetone to remove it, in fact I used my wife’s nail polish remover (since it doesn’t stink so bad) on some q-tips to get all the nooks and crannies cleaned out on the derailers.
Is it a good idea? I have no idea. I thought it looked nice. The “ultegra” lettering is painted on, so you have to avoid that if you want the lettering to persist. I left it on the rear derailer and polished it off the cranks.