Summary for rohs compliant black oxide Discussion
RoHS compliant black oxide is the central issue in this thread: John Andrews says his carbon steel parts are currently finished to MIL-C-31924, Class 1, but he believes that process is not RoHS compliant and wants an alternative for RoHS products. DLA questions what part of the coating is noncompliant, and John replies that the concern is the hexavalent chromium byproducts associated with the chromic acid dip. Willie Alexander explains that, when the specification is followed, Class 1 and Class 2 black oxide receive a chromic acid dip and are allowed to dry without rinsing, which is why the process can conflict with RoHS concerns. He suggests the customer might consider an exception to the chromic acid dip for this application. The discussion does not identify a fully RoHS-compliant black oxide process, but points to the chromic acid step as the likely issue.
Q. We are presently utilizing Black Oxide per MIL-C-31924, Class 1 over carbon steel (AISI 1026 and 1141). We have determined that this material is not ROHS compliant. Because these components are used in ROHS compliant products, we are seeking black oxide coating which is RoHS compliant.
John Andrews
– Murphy, North Carolina, United States of America
June 4, 2012
A. Hi John. That surprises me. Can you tell us what is in the black oxide coating that is not RoHS compliant?
Regards,
Ted Mooney, P.E.
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finishing.com – Pine Beach, New Jersey
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June 5, 2012
A. The material which makes the black oxide per MIL-DTL-13924
[⇦ this spec on DLA] non compliant with ROHS are the hexavalent chromium by products from the chromic acid dip.
John Andrews
– Murphy, North Carolina, U.S.A.
First of two simultaneous responses — June 7, 2012
A. Ted
If performed to the specification, the Class 1 (& 2)finish receives a chromic acid dip, and allowed to dry without subsequent rinsing.
John
Perhaps your customer would consider an exception to the chromic acid dip for this application.
Willie Alexander
– Colorado Springs, Colorado
Second of two simultaneous responses — June 7, 2012