Electropolishing removes a very thin layer of metal from a part in an acid bath with electric current, the reverse of plating. Peaks on the surface dissolve faster than valleys, so the part becomes smoother, brighter and easier to clean, with burrs removed. On stainless steel it also leaves a strong passive film, so parts resist rust and bacteria better.
Quick facts
- Materials
- Mainly stainless steel; also aluminium, copper, titanium
- Metal removed
- Typically about 5–40 µm, controlled by time and current
- Roughness
- Often improves Ra by roughly half
- Finish
- Bright, smooth, easy to clean
- Edges
- Fine burrs removed; sharp edges slightly rounded
- Usually priced
- Per part or per square metre
How it is done
- Parts are cleaned and mounted on racks that carry the current
- They are dipped in an acid electrolyte with the part as the anode
- Current flows for a set time; metal dissolves evenly with peaks going first
- Parts are rinsed, neutralised and dried
- Roughness is checked if the order gives an Ra limit
Electropolishing or mechanical polishing?
| Electropolishing | Mechanical polishing | |
|---|---|---|
| Reaches inside bores and corners | Yes, where current reaches | Only where tools reach |
| Leaves polishing compound or grit | No | Can, needs cleaning |
| Removes deep scratches | No | Yes |
| Best combination | Mechanical polish first, then electropolish | — |
What to send
- Material and grade
- Part drawing or photo, size and weight
- Starting finish and required Ra, if any
- Faces or threads that must be masked
- Quantity and how parts can be hung
- Whether passivation tests or a certificate are needed
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Questions
- Does electropolishing change dimensions?
- Slightly. It removes a controlled layer, usually about 5–40 µm, so close-tolerance sizes need allowance or masking.
- Will electropolishing remove scratches?
- It smooths fine roughness and removes small burrs, but deep scratches and tool marks stay visible. Polish mechanically first for a mirror look.
- Why is electropolishing used in food and pharma plants?
- The smooth, clean surface holds less dirt and bacteria and is easier to clean, and the stainless steel resists corrosion better afterwards.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 22 October 2026.