Electropolishing concentrations and current densities
I am looking for a recipe and process for electropolishing small 316 and 304 SS parts. This is essentially a hobby project. I believe that solutions of H3PO4 and H2SO4 will work but I don't know what the concentrations and current densities are. Also are there any caustic solutions that would be useful. I would appreciate any help or suggestions. Thanks.Mickey Palmer
Yes, the ware should be caustic cleaned before electropolishing. After rinsing, allow for drainage since water poisons electropolishing baths, causing them to etch.
I'd suggest you consult the Metal Finishing Guidebook, Electroplating Engineering Handbook, or Metals Handbook Volume 5: Surface Engineering; they all have good introductory chapters on electropolishing stainless steel, including compositions and current densities. Electropolishing requires high current density, and if it is not high enough, you'll only get etching, not polishing.
Electropolishing may not be a fun hobby, though! You'll be working with concentrated and dangerous caustics and acids. And you'll need to think about how to dispose of the solutions and the rinse water. You may wish to find a electropolishing job shop instead of doing it yourself if you object is just to get it done rather than put in weeks of work on a few parts. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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