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topic 2427

Zinc Deposit on Anode Baskets


(1998)

I recently started working with a zinc-cyanide plating system and have noticed a spongy type deposit on the titanium anode baskets. This deposit is dark gray and has an open/porous surface structure. It would appear as though this material is zinc that was dissolved from the anode but never quite made it into solution.

Can anyone tell me exactly what this material is, how it is formed, and if this is a problem or not?

Robert Holderman
Hilti


Doesn't sound very likely that it is zinc, in that I see no reason why zinc would dissolve from the anode balls, then redeposit at a point of higher anodic current density. Are you quite sure that it is a deposit, and not a manifestation of etching of the titanium?

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(1998)

I agree with Ted. Someone once told me that you shouldn't put titanium baskets in cyanide baths (or high chloride for that matter, like Woods strike). I have seen titanium hooks slowly disappear from copper anodes hanging in a cyanide strike bath. I have also removed the shreds of a titanium basket from a Woods tank.

However, on the outside chance that it is zinc, you might possibly have a bipolar situation where the zinc dissolves from one basket, or one side of the basket, and plates out somewhere else. Check the quality of the connections between the hooks and where they contact the buss rod, Clean these sites to be sure of a good connection.

bill vins
Bill Vins
microwave & cable assemblies
Mesa (what a place-a), Arizona 


(1998)

Ted and Bill thanks for the help. The bipolarity theory appears to make the most sense. We are truely observing something depositing on the baskets. My thinking that it is a zinc deposit is because of the color and the overall size of the deposits. I'll take a look at the connections to see if that is the problem.

Thanks again for the help. Bob Holderman

Robert Holderman
Hilti



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