Metal finishing Q&As since 1989

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Plating zinc contamination from sulfuric acid bath

Dear Sir/Madam,

I wish to plate out zinc contamination from an 8% sulfuric acid in water bath that we use to remove zinc oxide from brass extrusions. The zinc level is around 15,000ppm, although we start with clean liquid and over time it becomes contaminated. The reason for doing this is that we have limits on the zinc allowed in our rinse water stream and we commonly exceed these. Hence, if we continuously plate out the zinc from the acid then the rinse water will have very little zinc due tot the low carry over form the acid bath. I need to know the current density/voltage/plate material, area and separation, etc suggested to trial this technique.

Regards,

James Conner
AW Fraser - Christchurch, New Zealand
2002

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Plating out metals from wastewater is commonly done. It's done at low voltage with as high a cathode area as practical, sometimes even onto carbon or copper sponges. It also requires extreme agitation. Also, very tight anode to cathode spacing is needed, and therefore preventing short circuits is always an issue. What I'm saying is that constructing an efficient electrolytic recovery cell is much more of a question of solid engineering than of electrochemistry, and standard models are available from a number of vendors which would save you years of development effort.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002