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Electropolishing Rate

I am trying to speed up the electropolishing process of AISI 304 stainless steel parts as the process is currently too slow. From what I have read, it seems that the only way to speed things up is to remove the Fe ions from the acid solution. This apparently cannot be done through precipitation reactions owing to the low pH of the solution, the same with ion exchange resins. The solution of choice is a sulfuric acid/phosphoric acid base solution. Does anyone have any suggestions as to how to remove Fe from the electrolyte with such a low pH?

Thanks,

Janet Basson
- South Africa
2002

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Try bleeding off and dumping some electrolyte and replace it with fresh. Alternatively look for an electrolyte that precipitates out unwanted metal. Although 300 series electropolishing solutions are quite simple in principle, many suppliers add quite complex additives to remove unwanted metals and improve the life of the electrolyte. As the metal content of most baths increases, the performance can eb maintained by altering the operating conditions, especially the temperature, but this is only really a short term solution prior to dumping the bath. Talk to your supplier about consistent quality from the solution.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2002