Summary for bright acid tin plating Discussion
Bright acid tin plating is producing much thinner deposits at the same 100A amp-hours, with voltage rising from about 5V to 6.5–7V after a four-month pause. Jose Marquez says he already changed the solution, cleaned contacts, and replaced anode bags, but still sees a suspicious 6.1V reading between the negative busbar and the machine frame and wonders if the machine is shorted. In reply, the answerer says that neither anode nor cathode should be grounded, but static voltmeter readings can be misleading unless they are consistent; a true current leak is more likely if the reading is steady. He emphasizes that Faraday’s Law means the same current, area, and time should give the same thickness, so the problem likely lies in the setup or efficiency. He suggests checking for uninsulated heating or coiling coils, poorly insulated contact saddles, hot bus-bar joints, and using Hull Cell testing to determine whether the bath or plating efficiency has changed.
Q. Hi.
I’ve been evaluating bright acid tin plating. For my parameters, I’ve been using constant current of 100A with voltage of 4.9V ~ 5.1V. This parameters gives me good thickness. When I resumed my evaluation after 4 months, when I use 100A of constant current, I noticed that my voltage goes up to 6.5V ~ 7V, and my thickness becomes very low. I changed my solution since it very turbid as well as cleaning all contacts for any resistance and anode bags
⇦ huh? were replaced, but still the voltage is 6.5V ~ 7V. I tried measuring actual voltage using a multi meter and the voltage is the same with the display of voltage in the machine. One observation that bugs me is that when my negative probe of multi meter is tap in the negative terminal of busbar, and the positive probe is tap in body/frame of the machine, there is a voltage registered in multi meter, around ~ 6.1V. Is there any chance that my machine is shorted? Thanks.
Jose Marquez
– Abrantes Portugal
July 6, 2024
A. Hi Jose.
Although neither anode nor cathode should be grounded, such voltmeter readings often doesn’t mean much because if no current is flowing and we’re talking only “static” readings, they can vary quite a bit. A current leak is more likely if that voltage reading is consistent than if it bounces around.
Faraday’s Law doesn’t lie. If you’re applying the same current to the same surface area for the same amount of time, you should be getting the same thickness. I’d like to see you looking around for an uninsulated heating or coiling coil, or a contact saddle with bad insulation on the bolts, hot joints in the bus bar, etc.
Hull Cell ⇦ huh?
testing can probably tell you if there is a problem with the plating solution, as well as giving you the efficiency of the plating so that you can confirm what thickness you should be getting.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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