For those of you who do work with stainless steel and have any problems with free iron contamination or rust, here's an inexpensive way to deal with it. I've seen electropolishing machines for sale on the internet that range from $1500 to $3000, but you can build one yourself that does the same thing for cheap.
What you need:
-Power supply: My prototype used a laptop computer power supply, then I "upgraded" to this one:
http://www.provantage.com/tripp-lite-pr10~7TRTR01L.htm (~$65 delivered).
-Pair of banana plugs and 12 gauge wire for leads (~$15).
-Small ground clamp
-Polishing wand (I made mine from 3/4" pvc pipe): Anything non-conductive should work.
-Cathode: I used a 1" x 3" piece of stainless steel sheet metal fitted to the end of the polishing wand. I cut a slot in the end of the pvc, slid the sheet metal cathode into the slot, then ran a 1/4" bolt through the pipe and the cathode to hold it in place.
-Scotch-Brite or similar scrubber: Use pieces of the scrubbing pad to cover the cathode; secure with a rubber band or zip-tie.
-Acid-based cleaner: I use Walter E-NOX brand stainless cleaner.
Attach the ground clamp to one lead. Attach the wand to the other lead, securing the end of the lead to the cathode. Cover the cathode with the Scotch-Brite pad. Soak the pad with the stainless cleaner. Plug the leads into the power supply and turn it on. Attach the ground to piece you are cleaning, and rub the soaked cathode over the area you want cleaned. You'll see tiny bubbles form if it is working properly. Change your Scotch-Brite when it gets too dirty or worn out.
Make sure to rinse the cleaner from the piece you cleaned when you are finished. It only takes a few seconds to do the work and passivate the stainless material.
Now stand back and pat yourself on the back for saving yourself (or your company, in my case) a few grand!
