Metal finishing Q&As since 1989

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Electrodes polarity

Electrolytic dunk tank is equipped with four electrodes and sink roll (strip is changing direction).Supplied from rectifier switchboard (two rectifiers).Electrodes and strip are in order : electrode-strip-electrode, electrode-strip-electrode.Please, show electrodes polarity?

TURINA ZVONIMIR
DANIELI - BUTTRIO, ITALY
2006

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Depending on the process, the polarity could be either way, Turina. The information you have supplied does not change that, it just leaves us with some guessing.

So I would guess that there is no contact with the strip? If there is not, then the current must be induced into the strip.

If that is the case, then it is possible that the two rectifiers are in parallel, with one pole connected to the first two electrodes and the other pole connected to the last two electrodes. This would make the strip either positive on the downswing and negative on the upswing or vice versa. And if that is the case, then I would think that the "electrolytic dunk tank" is probably an electrocleaner rather than some other process. And if it is an electrocleaner, it is probably better to do cathodic cleaning first and anodic cleaning last. That means the strip must be negative on the downpass and positive on the up-pass. Finally, that means the first two electrodes are positive and the last two are negative.

I assume this is a homework question, not an engineering audit question since it would be much more practical to look at the bussing than to guess about it :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006