Electropolishing

Electropolishing smooths and brightens metal surfaces by controlled anodic dissolution, reducing microscopic peaks, improving corrosion resistance, and deburring without mechanical contact.

Overview

Electropolishing is an electrochemical finishing process that removes a thin, controlled layer of metal from the surface in an acid electrolyte. The part acts as the anode, so material comes off preferentially from micro-peaks, lowering Ra/Rz, removing embedded contaminants, and improving corrosion resistance and cleanability. It also knocks down light burrs and can create a bright, reflective finish.

Choose electropolishing when you need uniform micro-smoothing on complex geometry, internal passages, or delicate features where abrasive methods risk rounding edges inconsistently or trapping media. It’s common on stainless and nickel alloys for hygienic, medical, and high-purity service.

Tradeoffs: it removes material (dimension shift) and won’t fix deep scratches, waviness, or major tool marks—those need prep. Current distribution drives results, so sharp edges can “pull” and thin, and blind holes/cavities may polish unevenly. Masking, racking/fixturing, and documentation (ASTM/BPE/passivation requirements) strongly affect cost and lead time.

Common Materials

  • Stainless steel 316L
  • Stainless steel 304
  • Aluminum 6061
  • Titanium Grade 2
  • Inconel 718
  • Copper

Tolerances

±0.0002" to ±0.001" (material removal dependent)

Applications

  • 316L sanitary tubing and fittings
  • Medical implants and surgical instruments
  • Semiconductor gas panels and manifolds
  • Pharma process tanks and agitators
  • Aerospace fuel system components
  • Precision springs and fasteners

When to Choose Electropolishing

Electropolishing fits parts that need improved corrosion resistance, cleanability, or lower Ra without abrasive contact, especially in stainless and nickel alloys. It works well for complex shapes, fine features, and internal flow paths where uniform micro-deburring and smoothing matter. Plan it as a final finish after machining and any required cosmetic prep.

vs Manual Polishing

Choose electropolishing when you need repeatable surface quality over complex geometry, internal passages, or high part-to-part consistency. It reduces operator variability and avoids abrasive embedment, but won’t remove heavy stock or deep scratches as efficiently as aggressive hand work.

vs Lapping

Choose electropolishing when you need overall micro-smoothing and corrosion/cleanability benefits on 3D shapes rather than extreme flatness. Lapping excels at achieving very flat, tight-fitting sealing faces, while electropolishing is better for complex parts where conformal contact finishing isn’t practical.

vs Passivation

Choose electropolishing when you need both surface smoothing and corrosion performance improvements. Passivation mainly enhances the oxide layer and cleanliness with minimal dimensional change, while electropolishing actively removes metal and can materially improve Ra and deburring.

vs Vibratory Finishing (Tumbling)

Choose electropolishing when media entrapment, part-on-part damage, or access to internal passages is a concern. Vibratory finishing can be lower cost for external deburring at scale, but it struggles with internal features and can round edges unpredictably.

Design Considerations

  • Call out allowable material removal (or max thickness loss) and critical dimensions that must be protected
  • Remove deep tool marks before electropolish; specify pre-polish level if cosmetic finish matters
  • Avoid very sharp edges and thin webs where current density can over-polish; add small edge breaks where acceptable
  • Minimize blind holes and deep, narrow cavities or specify areas that can be excluded/masked due to uneven polishing
  • Provide clear racking/fixturing surfaces and identify cosmetic/non-cosmetic faces to control contact marks
  • Specify the required standard and verification method (e.g., ASTM B912, ASME BPE, target Ra and measurement location)