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ELECTROPOLISHING CAST CF8M (316 ss)

I'm having a terrible time electropolishing cast CF8M (316 SS). The part is a typical 1/2" flange valve with an internal water passage. The problem takes place in the water way. When the parts come back from the electropolisher they look fine on the outside, but nothing seems to have taken place along the entire internal passage way of the valve. The electropolisher tells me this is related to electrical chargers and the only way to eliminate it is with extensive tooling setups. Any advise would be appreciated.

SHAWN MCKINNEY
- EPHRATA, Pennsylvania
2002

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Shawn,

I have experienced the same problems and your electropolisher is correct they would have to actually fixture an electrode down in the water passageway of your valve(with out touch the side walls) in order to get the finish that you desire. That would be very expensive.

There are many other treatments that can be done. I would recommend a pickling process first to remove any contaminants and then a passivation process using a citric acid bath....this bath can provided you with a very clean part inside and out and the appearance was very close to what we where getting during electropolishing (depending on which casting process was used to make your part, some don't get that luster appearance)

But, for your sake, it would be worth it to try some samples and talk to a metal improvement specialist to be sure your achieving what your looking for on your parts. Oh ya, the pickling and passivation should be cheaper too...it takes a lot of current($$$$) for the electropolishing process as compared to a timely bath in citric acid .

Regards,

Keith Osborn
- Mentor, Ohio, USA
2002