DIY - Electropolishing

Tony -
Here's a screen shot from the link you provided:
Screen Shot 2018-04-12 at 3.09.32 AM.jpg
Given the high rotational speed required to get "very high G-forces," and the masses involved (not just the parts and polishing media, but also the strength required of the barrels to resist the G-forces), I'd say it would be difficult to scale this process down for home shop use. Durn!
 
Tony -
Here's a screen shot from the link you provided:
View attachment 264776
Given the high rotational speed required to get "very high G-forces," and the masses involved (not just the parts and polishing media, but also the strength required of the barrels to resist the G-forces), I'd say it would be difficult to scale this process down for home shop use. Durn!

We have the HZ-12 in our plant. It's about a $15,000 unit. The barrels are about 3/8" thick wall steel containers and are lined with urethane. We run our stainless steel parts in these for about 45 minutes and large burrs and edges from stampings are completely gone and parts have a uniform finish.
 
After I posted in April, I did some experimenting with hexavalent chromium (aka chromium VI or Cr VI). It is easily reduced to chromium III by the addition of iron filings. Chromium III (in small amount) is not harmful and is in fact an essential part of our diet. It is used as treatment for type 2 diabetes by enhancing insulin effectiveness.

If you have concerns about disposing of any solution which you feel may contain hexavalent chromium, throwing in a handful of iron filings or turnings and allowing it to sit for a few days should take care of it.
 
Great news! Thanks.
... not that I plan to do any electropolishing in the foreseeable future, but it's always good to know that there's a safe, easy means of detoxifying the waste.
 
Hexavalent chromium is an extremely powerful oxidizing agent. I recall a demonstration of this during a fire training session at work. The trainer made a small pile of chromium trioxide crystals, then -- from a safe distance -- sent a stream of acetone at it from a squirt bottle. The acetone instantly burst into flame! This was done outside on a paved parking lot. The point being Cr+6 is very happy to go to a lower oxidation state, and that's why something like (fresh) iron filings works to reduce CR+6 down to something less toxic.

The demo was done back when regulations on things like Cr+6 were considerably looser than they are now. A demo using the same stuff just isn't happening these days.

Even now, chromium trioxide is a component of some types of metallurgical etches. Getting rid of the spent etch solutions costs more than the fresh chemicals. You can't store them in glass because many also contain hydrofluoric acid, which attacks glass. And plastic bottles exposed to it eventually develop pinhole leaks.....or worse.
 
Back
Top