What is the size & quantity of your parts?
Are you looking to spend $7500, $75000 or $750000?
Need acid resistant tanks, pump & heater, chemical storage, wastewater treatment, EPA permits to store, use & treat hazardous chemicals.
[Note: There are proprietary, non-hazardous solutions available -- see
-- but the license for one is $75000.]
It's probably best to have a commercial electropolisher do your parts, but here are some basics to help decide.
General purpose bath for SS & Ni-base alloys:
Bath: 65 wt% sulfuric acid*, 15% phosphoric acid*, 22% DI water. A little surfactant helps in wetting the surface and reducing bubble size of gas (O2) produced at the part.
*These are absolute concentrations as determined by titration and specific gravity. Commercial sulfuric is 93%, commercial phosphoric is available in 75% or 85% (preferable) concentrations.
You can also use a commercial bath, e.g.,
At least, read their process info.
Another informative site for "Electropolishing Basics" is
Temp: 80-175 F (130-160 F preferred).
Voltage: 6-12 Volts as needed to supply a current > 50 Amps/sq. ft (100 Amps/sq. ft is preferable).
Time is 1-15 minutes (best determined empirically for a given anode/cathode geometry, solution & electrical parameters).
Need to preclean parts; electrocleaning is best (but not required).
Parts are anodic. Copper cathodes work best, but I suggest removing (with rinsing) when not in use. Sometimes can use Cu sheet, but need to avoid trapping gas bubbles which cause streaks on parts, dull white areas if trapped. Surfaces to be polished should be nearly vertical but facing upward. Sometimes, need to mask off surfaces, & do parts in 2 steps.
A uniform anode-cathode distance is important, e.g., 1". Sometimes, use polypropylene standoffs [and brush EP tthe covered area afterwards].
You may need heavy copper mesh bolted to a framwork of 1x0.25" bars to conform to a curved part and allow gases to escape. Silicon bronze fasteners last longer than Cu. Make sure the exposed threaded ends face away from the part surface so as not to scratch. Solution agitation, either by mixer or pumping (but not air) is recommended.
Best to spray rinse with DI water as withdrawing the electropolished parts from the bath, then go through a 110 F dragout rinse (captures hazardous metals & acids) & a flowing rinse to remove the sticky EP solution.
Remove any Cu connectors.
Place in a 25-45 vol% nitric acid solution for at least 10 minutes to remove residual sulfates & phosphates & Cu & to passivate the surface.
Rinse, rinse, warm DI rinse & dry.
Handle electropolished parts with white cotton gloves.
Let us know what you decide to do or if need help with specific problems.
Ken
