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Letter 41067
Hexavalent Chromium, how do I test for it
on fasteners
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I am a fastener distributor in Chicago, IL & with the
evergrowing need to have parts be ROHS Compliant, I would like to
either create or purchase a test kit for the detection of hexavalent
chromium on zinc & zinc/aluminum alloy coated steel. Do you know
of any test methods currently out there???
Tony Keas
hardware & electronics - Chicago, IL
++++++
Rohs compliance can be tested by following a procedure set out in
GM spec 3044W. You can probably buy the test kit from a local
company, Kocour. Be advised, that using this test some products can
give a false positive. The more accurate method is to send a sample
of the batch to a lab for testing using an ICP. Generally, most end
users rely on a certificaton from the plater stating that the finish
is RoHS, WEE or ELV compliant. The alternative statement the finisher
might make is that the part does not contain hexavalent chromium.
Gene Packman
- Great Neck, NY
++++++ -- appended to this existing thread by editor
in lieu of spawning a new thread
I want to know by looking on to any component how we can
understand that whethet it is Trivalent Chrome or Hexavalent Chrome
or If any other verificaion method available for the same.
Navin Sobhani
controls & switchgear - Noida, India
++++++
Another option is to try portable x-ray fluorescence (XRF) for
your fasteners that are out in the shop. But keep in mind that
neither XRF nor ICP (in the lab) can distinguish between trivalent
and hexavalent Cr coatings. If you know what else is in the Cr
coating you might be able to look for that species, but that is an
indirect way of doing things.
Terry Tomt
- Auburn, WA
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Cr 6+ can reduce sodium thiosulfate solution (iodometery).But Cr
3+ can not reduce above solution.
Garshasb Mir
- Esfahan, Iran
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The only method which can tell the difference between Cr6 or Cr3,
is by an indicator named diphenyl carbazide. The point is that it has
to be freshly made up.
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Sara
Michaeli
chemical process supplier
Israel
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++++++
Sara,
The method you refer to will give a false positive in the prescence
of iron, cadmium, zinc or several aldehyde compounds. That is the
reason why the ICP method is suggested. The testing is done similar
to waste water where trivalent and hexavalent chromium are seperated.
The protocol for this test is spelled out in the specs from National
Semiconductor among others.
Gene Packman
- Great Neck, NY
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