Letter 058

Seeking info about electropolishing stainless steel

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I would like to find information regarding the process for electropolishing stainless steel. This is for a hospital equipment manufacturer, and we need it to eliminate the actual process which is by abrasive polishing after TIG welding in order to remove the black residue produced. I've heard that by reverse electrolysis you can achieve very nice finishes.

Hope to hear from anyone soon. Thank you   Federico  

FEDERICO JAVIER RODRIGUEZ CAVADA
Mexico

The American Electroplaters and Surface Finishers Society (www.aesf.org) has a very good 'Illustrated Lecture' on electropolishing; the Electroplating Engineering Handbook (Van Nostrand Reinhold) has a very through treatment of it; and the Metal Finishing Guidebook covers it well too.

Basically, the stainless steel is immersed in a strong acid at a high current density and the asperities are dissolved away--leaving a very smooth, burr free, passive, surface. It's not necessarily an easy or cheap process to run, but it is definitely a great way to finish stainless steel.

Ted Mooney, P.E.  finishing.com Brick, New Jersey +++++ In electropolishing is it possible to achieve mirror finish on stainless steel 316L grade material. Component has got cavity shaped like "W". Thanks Robert Denso - St,luid, Missouri ,USA +++++ St. Luid, Robert? Is that near San Pomme de Terre? I don't think 316L is any special problem. The component probably can be electropolished despite the W-shaped cavity, but it may require customized fixturing because you have to get current down into the bottom of that "W" and you need to avoid hydrogen gas accumulation, or stratification of the solution, Ted Mooney finishing.com Brick, New Jersey