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"Chromium in my Anodizing Waste?"

April 14, 2021

Q. I am running a sulfuric acid anodize line anodizing 6061 and 7075. I have a problem with very high levels of chromium in our waste (A highly regulated RCRA metal in the US). We currently ship this off as Hazardous Waste. As I read through the forum, nobody seems to have this problem. I can't imagine that I am the only anodizer with this problem. Or maybe nobody else has tested their waste for RCRA metals? Anyone have any ideas where this might be coming from?

Randy H.
- Sanford, North Carolina

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April 2021

A. Hi Randy. Assuming you are doing no chromate conversion coating (Alodine. Iridite), no chromic acid anodizing along with your sulfuric acid anodizing, and no chrome sealing, I don't understand it either.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

July 16, 2021

A. There is Chromium in some if not all Aluminum alloys; and in the anodizing process, the alloy is dissolved adding Chrome to the solution.

Have the Anodizing solution checked for Chrome along with the Aluminum, and decant before it is above your limits.

John Sadis
Environmental compliance Mgr - Mukilteo Washington

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