Letter 039

Insoluble anodes to prevent metal buildup in acid zinc?

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Our zinc metal keeps growing in our rack line. We have tried all the usual fixes. Has anybody tried to use insoluble anodes to drive the metal down without destroying the brightener? This is a chloride zinc bath 16 oz./gal. Hoping for a 21st. century answer. Thanks, --Frank      

Frank Z
- Paterson, NJ

No, I've never heard of insoluble anodes for zinc, but you might try elevating the pH a little with potassium hydroxide. See how it works in a Hull cell.

Dave Wichern - Bronx, NY, USA

  

I hope that when you say that "This is a chloride zinc bath 16 oz./gal." that you are referring to the KCl level and not the Zn metal level. You could try platinized titanium or iridium oxide coated titanium anodes. Bare titanium will become passive and not conduct current. It is pretty expensive stuff, though. I have found Cosmos (Mineral Corp.) to be very helpful in obtaining this material on short notice. I'm not sure, though, what will be the relative resistance between this material and standard zinc anodes. If they do not conduct current similarly, you could find the current preferentially going through one or the other anode material. You would have to try and do some experimenting. Ken      

Ken Rosenblum
finishing shop - Minneapolis, Minnesota

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