I’ve got some black rotor chainrings I want to use on a “classic” styled bicycle that would look far better if they were silver/plain metal. I’m thinking of stripping the anodizing, but I’m not sure if that will mean the chainring will wear more quickly. I seems difficult leave the finish on the teeth but not the face of the chainring - I think i’d have to dip the whole component. (and I don’t think i want to hand-sand the whole chainring…)
I know that TA chainrings don’t have anodized teeth and their face anodizing is cosmetic only (but do they have a clear finish on the teeth (is that possible?). Quote:
http://www.poshbikes.com/make.php?22]“Each chainring is machined, polished, and anodised, after which the tooth profile is re-machined for perfect pitch and alignment. (No colour anodising to wear off the teeth first time out!)”
But would that be the case for the rotor chainrings I have? Any pointers? I’d be keen to have my bike look good, but not if I end up turning my not-so-cheap chainrings to cheese.
This is what my crankset would look like - you can see that the anodizing is coming off the teeth on the pictured chainrings - I’m not sure how much of a contribution it makes to wear life… given it seems to wear off pretty quickly around the edges of teeth on all similar (mtb) chainrings I’ve used but does seem to persist for a good while on the wearing surface of the teeth.
Ive read that the chemical reaction of annodising on the surface has another effect that strengthens/protects it against scrapes etc. might be a myth or possibly not that noticeable.
There was a handy thread before of polishing parts which included removing the annodising, perhaps if you ask there if anyone has noticed a difference in scrapes/marks showing.
Most anodizing is just for appearance. Raw alu needs to be polished periodically otherwise it will dull and can corrode. There is some hard-anodizing that can add strength (and maybe make it brittle). The biggest factor in long wearing aluminium is what type of material it is and not anodizing.
That’s just my take. I’m not a scientist, or an engineer.
Al2O3 (Aluminium oxide) is harder and more wear resistant than aluminium, but as far as cosmetic anodising goes, forget about it. Don’t even bother trying to keep the anodising on the teeth, it will wear off very quickly.
Dip your rings in a caustic bath (drain cleaner, NaOH), don’t forget about them as they’ll pit and corrode something fierce. Then polish / burnish as required.
Bear in mind anodised chainrings will only need a quick 5 minutes in a caustic solution and will not affect the integrity of the alu. Hard Anodised will need a helluva lot more time and repeated baths to get the stubborn shit off!
Thanks for the feedback guys. The rotor propaganda says that the chainrings are “Hard anodized for ultimate endurance”… Does this change things? I have no idea if this statement is anything more than marketing BS and if the anodising should be considered nothing more than cosmetic? (Blakey?)
As an aside, these chainrings look pretty kooky - the big ring is very obviously elliptical, but the little ring is ever so subtley so. Can’t wait to see how they ride.
I would be careful putting Aluminium into some caustic solutions. I did this with a spray gun to remove some dried paint and it really ate into the Aluminium and covered it with a black tarnish. Not good. Do you need to do this? I think you might be better off getting a new chainring maybe.
Anodizing is a pretty commonplace process intended to protect aluminium from corrosion. I have found it to work. I don’t think that it is just marketing speak.
Yeah, if Rotor sold a Shimano OCP3 chainring in silver, I’d have bought it… but sadly they don’t.
The black tarnish left after stripping can be brushed off and polished up I believe, but yes, serious corrosion is not good. How dilute was the solution you used - sounds like it might’ve been too strong?
