costa - 18-10-2004 at 13:20
Is the chromium found in aluminum 6061-T651 or 5052-H34 hexavalent form? Europe is placing a ban on hexavalent Cr and we need to determine if the
aluminum we use is impacted.
Thanks
Costa
(see http://www.aerospacemetals.com/aluminum.html for technical data)
chemoleo - 18-10-2004 at 13:53
You are talking about an ALLOY!!
Which means, it is a mixture of elements, here chromium and aluminium, and NOT a mixture of Al and a chromium SALT (which hexavalent chromium would
be).
Both Al/Cr are in their free elemental state, so the Chromium has no formal charge.
Hence Al-Cr alloys do NOT contain Cr VI+.
So no need to worry here. If anything, the photographics industry will be impacted... and of course poor fools like us 
Nerro - 14-11-2004 at 05:01
Kiss your dichromate goodbey.
Does this also impair the superconductor industry? I think they use Cr in some of the experimental ceramics.
Jen - 19-11-2004 at 13:36
I doubt the semiconductor industry would worry because a) if they're going to be introducing it as a dopant, it will be in pitifully small
quantities b) as far as I know it's only the use/disposal of aqueous hexavalent ions that they're worried about. People try to steer away
from making dissolvable semiconductors or ceramics as it kind of defeats the point.
I'd be more worried about the fact that they don't actually know how hexavalent Cr works, and they haven't got anything to replace it
as far as corrosion protection goes. Every plane you have ever flown on, has (probably) been treated with hexavalent chromium to prevent problems
such as pitting corrosion in aluminium.