Summary for hexavalent chromium in aluminum alloys Discussion
RoHS hexavalent chromium in aluminum alloys is the central question here: Costa Christopoulos asked whether the chromium in 6061-T651, 5052-H34, and similar aluminum alloys counts as hexavalent chromium for EU RoHS limits. Toby Padfield answered that it does not; when chromium is alloyed into aluminum, steel, and similar metals, it is not present in the hexavalent ion form. A later reader, Apostolos Tsirgotakis, asked in 2023 for more information, but no additional technical correction or contrary view appears in the excerpt. The practical takeaway is that the chromium in these common aluminum alloys is treated as alloyed chromium, not hexavalent chromium, for the purpose discussed in the thread. The excerpt also shows a later unrelated mention of MIL-A-8625, but no further answer is included.
Q. For the purposes of the New EU Directives and RoHS compliance, a maximum concentration value of up to 0.1% by weight in homogenous materials for hexavalent chromium will be permitted in the manufacture of new EEE.
Is the Chromium (Cr) found in 6061-T651, 5052-H34 or other common Al alloys hexavalent form? (please refer to https://www.aerospacemetals.com/aluminum-distributor.html for aluminum specs)
Costa Christopoulos
RoHS & WEEE – Montreal, Quebec, Canada
2004
A. No, the Cr is not present in the hexavalent ion form when it is alloyed with Al, steel, etc.
Toby Padfield
Automotive module supplier – Michigan
2004
Q. Good morning Costa. Did you finally find an answer on your question about chromium hexavalent. We are aluminium producers in Greece and I’m also interested on that topic. Can you please share some information with me?
Best regards,
Apostolos Tsirgotakis
– Paralia Distomou
August 29, 2023
Q. Currently we are specifying MIL-A-8625
[⇦ this spec on DLA] Type II for an anodize finish on 5052-H32 and 6061-T6 aluminum components in order to meet RoHS compliance requirement. A question comes up whether 5052 or 6061 themselves are RoHS compliant because of the amount of chromium in the base alloy material. I understand that there are 3 types of chromiums – zero valent, trivalent and hexavalent. Can anyone tell me what type of chromium is inside 5052 and 6061 alloys and if they are RoHS compliant? Thank you very much.
Jacky Yam
– Hazelwood, Missouri, USA
July 3, 2014
A. Hi Jacky,
Although when chromium is ionized in solutions and in salts (including chromate gels) it may be in the trivalent or hexavalent state (possibly even the divalent state), actual metals like chromium are in the metallic state, oxidation state 0. And in the general case like atmospheric corrosion, chromium metal will oxidize into trivalent form.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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