Tom, Thanks for the reply (below). The black marks in my crankset are not pits (small voids from corrosion), only speckled discoloration. I am familiar with how aluminium can corrode leaving a rough finish but that is not the case here. I have worked with aluminium parts on automobiles and as a fan and owner or Peugeot PX10's, the Stronglight 93 crankset and Mafac brakes are two examples of unanodized parts which are quite easy to keep looking good; I've never seen black specks these or in other aluminium parts but another lost member emailed me saying that his Campagnolo Mexico'd crankset has the same discoloration in it too. So, while I agree that corroded aluminium is very difficult to make good again, I believe these speckled cranks have some other problem. Any other thoughts?
Eric Elman
Somers, CT
>
> The black speckles are pitting and are typical of un-anodized aluminum
bike parts. On SR/NR stuff these parts include the shifters, ft der,
clamps, pedal bodies, hub shells, and seat posts. Rear hubs and 'posts are
particularly troublsome since they tend to see the most sweat from the
rider. I'm certain that unanodized cranks would be a real nightmare to keep
looking good. My experience is that pits are very difficult to remove.
They are much deeper than you might expect. I've had posts that I sanded
down, starting with coarse (!) emery cloth and moving to finer grits, then
Scotchbrite pads and 0000 steel wool, finally finishing with Flitz polish.
After all that, many of the pits remained. I'd say learn to live with the
pits, and keep them in check by wiping down the cranks after each ride. A
mild ammonia solution (Windex) is helpful, I think because of some ion
exchange process.
> Tom Dalton Bethlehem, PA
> Eric Elman <tr4play@cox.net> wrote: > 6. Lastly, my set is all polished
aluminium but despite how much I polish
> and buff them they have darker "stains/speckles" about the size of crushed
> pepper in them that will not come out. The stains are only noticable when
> you look closely but are there none the less - any ideas on the cause and
> any possible way to eliminate these dark marks?