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Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Removal of Cadmium from wastewater

Our plating solutions are all RoHS compliant. We do not do any cadmium plating, but I have noticed cadmium running through our wastewater system. Our wastewater after being treated pumps through ionization canisters filled with SCN resin. We are below the city limit but I am baffled where the cadmium is coming from since all our solutions are RoHS compliant.

Sahand Shafiee
Plating Shop Employee - Portland, Oregon
August 12, 2010

Hi, Sahand
The first thing I would suspect is that you inadvertently stripped some cadmium plated parts that you thought were zinc plated. Has anyone sent you parts for rework that were done by another plater? I would only strip parts that were plated/manufactured in China after careful study and if compensated very well. Even children's jewelry from China is made largely of cadmium, so anything could be.

If that is not the case, but you do Electroless Nickel, investigate carefully whether there is cadmium in your solutions. Only relatively new electroless nickel baths would be free of cadmium. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 12, 2010

August 12, 2010

I could be very wrong, but wasn't cadmium discovered in mined zinc? If so, your zinc anodes may have a trace of cad in it.

James Watts
- Navarre, Florida

Our electroless nickel baths are RoHs compliant. And we do not specialize in zinc plating and most parts we receive do not have zinc plating that has to be stripped off.

Sahand Shafiee
- Portland, Oregon, USA
September 2, 2010

September 3, 2010

Sahand

Just because your EN baths are RoHS compliant, does not mean they are cadmium free; only that they will produce a coating that meets RoHS. Cadmium (if I recall correctly) needs to be .01% of the article so you could still have a fair amount present in solution.

Have you tested it to be sure?

Willie Alexander
- Colorado Springs, Colorado

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