Dan: This is exactly the scenario or chain-of-logic that I am concerned
about! as it leads to the conclusion that any residual CrVI in the
treatment layer could be deemed illegal!
jw
Jerry Wagner Dept 0056 Environmental Engineering B096-1
x56275 pg 58888-0658 (607)755-6275 fax: (607)755-6282
Huron Real Estate Associates, LLC and Endicott Interconnect Technologies,
Inc.
Via the Internet: [log in to unmask] [NOTES: Jerome Wagner/Huron/EIT]
"Kallin, Dan"
<[log in to unmask] To: [log in to unmask]
COM> cc:
Sent by: Leadfree Subject: Re: [LF] Chromate conversions
<[log in to unmask]
>
02/20/2004 01:52
PM
Please respond to
"(Leadfree
Electronics
Assembly Forum)";
Please respond to
"Kallin, Dan"
The automotive customers compliance with ELV requires us to eliminate the
use of Hex chrome coatings pretty much across the board. Perhaps this will
be clarified or improved when "homogeneous material" is clarified, but if
they follow the lead of ELV (Which I have heard they are doing) the coating
would be considered the homogeneous material and therefore the 1000 ppm
would apply to the coating, not the coated part.
Clearly it is intentionally added as well, so the 1000 ppm limit probably
would not apply either.
__________________________________________
Dan Kallin Environmental & Safety Engineer
Bose Corporation Framingham, MA 01701
[log in to unmask]
508-766-7136 (phone)
508-766-7086 (fax)
__________________________________________
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Friday, February 20, 2004 10:26 AM
To: [log in to unmask]
Subject: Re: [LF] Chromate conversions
I don't understand the problem. Chromate conversion coating is usually
about 1 µm thick. Less than 1/3 the weight of zinc chromate is chromium.
The density of ZnCrO4 is roughly 1/2 that of steel. So if your steel is
more than 0.33 mm thick (assuming both sides are conversion coated),
then you will be under the 0.1% limit for flat surfaces. As hardware
with a convoluted surface, such as screws, is usually pretty bulky, I
see no problem there. You could always weigh your parts, chemically
dissolve the conversion coating and analyse to determine the weight of
chromium: I'll bet a pound to a penny that very few items (very small,
thin, convoluted parts) would exceed your 0.1%.
If you have transparent, colourless, chromate conversion coatings, these
must be very thin (less than 1 µm). Zinc chromate is a quite deep and
intense yellowish colour.
If you're still scared, there are other conversion coatings, such as
oxidation and phosphatation.
Brian
to Paul Taylor wrote:
> Dear All
>
> this question is a more RoHS orientated, however it is associated with
> metallurgy, I'm a bit confused as I'd not heard of it before.
>
> What chromate conversions involve Hexavalant Chrome (this applies to
> fixings, screws etc). I've been told that both the Nickel Plate and
> Zinc Chromate platings use Hexavalant chrome. Is this true? or have I
> been miss-informed.
>
> The issue fo us especially concerns steel parts that have a zinc
> chromate finish. This is also known as zinc clear and /or zinc clear
> chromate. The problem is that this process results in the part having
a
> coating of Hexavalent VI chrome. I am not a metallurgist, but have
been
> informed that when tested, the directive of having no more than 0.1%
by
> weight will be exceeded, by parts large in surface area.
>
> regards
>
> Paul
> Paul R Taylor
> Technical Advisor
> Pitney Bowes Ltd email: [log in to unmask]
>
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