Electropolishing

Electropolishing uses controlled anodic dissolution to smooth, deburr, and passivate metal surfaces, producing very low roughness and excellent cleanliness on complex geometries.

Overview

Electropolishing is an electrochemical process that removes a controlled layer of metal from the surface, preferentially leveling high points and burrs. It produces a bright, smooth, and passive surface with very low roughness (often <10 µin Ra) while improving corrosion resistance and cleanliness. It reaches internal passages, small radii, and complex geometries that are impractical or impossible to access with mechanical polishing.

You should consider electropolishing when you need clean, smooth, deburred, and corrosion-resistant metal surfaces on stainless steels, nickel alloys, or titanium, especially for sanitary or high-purity applications. It is common in medical, food, pharma, vacuum, and semiconductor hardware where surface condition drives performance and regulatory compliance. Tradeoffs: the process removes material and can slightly round sharp edges, it will not remove deep scratches or machining marks by itself, and it requires consistent incoming surface finish for repeatable results. It is limited to conductive metals and needs part-specific fixturing and process development, which add setup cost but pay off for repeat production.

Common Materials

  • Stainless Steel 304
  • Stainless Steel 316L
  • Stainless Steel 17-4 PH
  • Inconel 625
  • Titanium Grade 2
  • Titanium Grade 5

Tolerances

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Applications

  • Surgical instruments and implants
  • Biopharmaceutical tubing and fittings
  • Food processing equipment and tanks
  • High-vacuum and UHV chambers and components
  • Semiconductor gas lines and valves
  • Precision stainless springs and wire forms

When to Choose Electropolishing

Choose electropolishing when you need very smooth, clean, and passive metal surfaces on complex or hard-to-reach features, including IDs and intricate geometries. It suits repeat production of stainless and high-performance alloy parts for sanitary, medical, vacuum, or corrosion-critical applications where surface finish and cleanliness matter more than tight dimensional control. It is ideal when you need simultaneous smoothing, micro-deburring, and passivation in one step.

vs Manual Polishing

Pick electropolishing over manual polishing when you have complex geometries, internal passages, or higher volumes where consistent finish and repeatability matter. It reduces labor, eliminates operator variability, and can treat all surfaces uniformly, but requires accepting some material removal and edge rounding.

vs Lapping

Choose electropolishing over lapping when you need global surface smoothing, deburring, and corrosion improvement rather than ultra-flat mating surfaces. Electropolishing handles internal surfaces and complex shapes in batches, while lapping is better for precision flatness on accessible faces but is slower and more geometry-limited.

vs Vibratory Finishing

Electropolishing is preferable to vibratory finishing when parts are delicate, have fine features, or include blind holes and IDs that media cannot reach. It provides cleaner, more uniform micro-deburring and a chemically passive surface without the risk of media lodging or impact damage.

vs Abrasive Blasting

Select electropolishing instead of abrasive blasting when you need a smooth, bright, low-Ra surface and improved corrosion resistance, not a matte texture. Electropolishing removes embedded contaminants and smear, whereas blasting can embed media and increase surface area, which may hurt corrosion and cleanability.

vs Chemical Etching

Use electropolishing over chemical etching when you want controlled smoothing and brightening rather than patterning or aggressive bulk removal. Electropolishing is more uniform and predictable on edges and surfaces, with better deburring and passivation for functional parts rather than just surface texturing.

Design Considerations

  • Specify required surface roughness (e.g., max Ra) and cleanliness level rather than vague terms like ‘bright polish’ to help the shop set the right process window
  • Allow for uniform material removal on all electropolished surfaces in your dimensional stack-up; assume on the order of 0.0001–0.001 inch per surface depending on spec
  • Avoid sharp knife edges and extremely thin walls where small material loss or edge rounding could make the feature nonfunctional
  • Minimize deep machining marks, scratches, and pits; electropolishing will smooth but not remove deep defects, so plan appropriate pre-polish machining or grinding
  • Include generous radii and avoid very tight, blind crevices where solution flow and current distribution will be poor, leading to uneven finish
  • Clearly identify areas to be masked or kept dimensionally critical on the drawing so the shop can plan fixturing, masking, and inspection accordingly