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Stainless Steel Electropolish Tank Maintenance

Hello, and thanks in advance for any info/help you can give me.

I have started a new job at a small company who makes parts for customers in the semiconductor industry, where I'm most focused is on their electropolishing step. Currently they are using a purchased chemical that contains phosphoric and sulfuric acids. Right now they are only performing specific gravity testing on the tanks. They don't do huge batches at at time, and when they are internally polishing the parts they are only doing one at a time.

My question is: what is the best maintenance plan for these tanks? I've read on here somewhere that in addition to specific gravity testing there should be titrations done and a dissolved metal analysis. And what should I be looking for?

On a side note, I'm not sure that the ventilation on the tanks is up to where it should be, does anyone know what the cfm should be for open tanks?

Thanks again for any help!

Angie Wicklund
Chemical Tech - Sauk Rapids, MN, USA
January 9, 2008

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Hello, Angie. You are apparently using a proprietary electropolishing process. In general, proprietaries cost more than generic processes but offer the advantage of support from the supplier. At the least your vendor will offer a "technical data sheet" with recommendations. In addition, most of the general plating texts offer at least some coverage of electropolishing; the Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon] has a good chapter.

Required ventilation rates are based on a number of things including the hazard of the chemicals, but the "aspect ratio" is so critical that a recommended CFM cannot be offered without it. Aspect ratio is the length over the width. If your tank was, say, 6' x 2' and you had exhaust hood(s) running along the 6' dimension, the aspect ratio would be .33 and it would be relatively easy to ventilate. If the hoods were along the 2' dimension, the aspect ratio would be 3, and extravagant ventilation rates would be required. Best to send a sketch and a photo to an experienced exhaust system builder like KCH Engineering. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January , 2008