Electropolishing

Mirror surface.
Enhanced passivation.
Pharma-grade clean.

Electropolishing is an electrochemical reverse-plating process that removes a thin surface layer of metal, producing mirror-smooth surfaces with enhanced corrosion resistance. Standard finish for pharmaceutical, food, semiconductor, and medical applications.

Electropolishing Quote All finishes

Ra 0.1 µm Enhanced passivation Bioburden reduction 316L / 304 / 17-4 PH

01 · What it is

How Electropolishing works.

Electropolishing uses electric current and an acid electrolyte bath to dissolve a controlled layer (typically 10–25 µm) of surface metal from a stainless steel part. Unlike mechanical polishing which smears surface material, electropolishing removes it — revealing a mirror-smooth surface with no residual smearing, embedded abrasive, or stress.

The process preferentially dissolves surface peaks (high points) faster than valleys, leveling the surface to a mirror finish. It also selectively removes iron preferentially to chromium, leaving a chromium-enriched passive layer that provides superior corrosion resistance compared to mechanically polished or passivated surfaces.

Beyond cosmetic appearance, electropolishing provides functional benefits: reduced biofilm adhesion (medical/pharma), reduced particle shedding (semiconductor), enhanced corrosion resistance (marine/chemical), easier cleaning (sanitary applications), and reduced surface friction for flow-critical applications.

02 · Specifications

Capability specs.

Ra 0.1 µm

Surface finish

Typical electropolished finish. Mirror appearance, measurable via profilometer

10–25 µm

Material removed

Layer of metal dissolved in process. Adjust mechanical dimensions accordingly

+30%

Corrosion improvement

Salt spray resistance vs mechanically polished. Chromium-enriched passive layer

SS only

Material compatibility

Stainless steels primarily (304, 316L, 17-4 PH). Not applicable to Al or Ti

Any size

Part size

From 5 mm fittings to 2 m fabrications. Tank size is the practical limit

Pharma grade

Cleanliness

Meets ASME BPE sanitary requirements for pharma tubing and hardware

FDA compliant

Process chemistry

Bath chemistry and rinse procedure compliant with FDA sanitary requirements

Eliminates

Machining burrs

Deburring is automatic — electropolish removes burrs as it polishes

03 · Applications

Where Electropolishing excels.

Pharmaceutical tubing

BPE-compliant stainless tubing for sterile pharmaceutical processes

Medical instruments

Reusable surgical tools, biopsy needles, orthopedic instruments

Food contact

Sanitary food processing equipment — tanks, mixers, transfer hardware

Semiconductor handling

Wafer carriers, vacuum chamber internals — reduced particle shedding

Implantable medical

316L bone plates, fracture fixation — improved biocompatibility

Marine hardware

316L marine hardware — enhanced salt-water corrosion resistance

Chemical processing

Chemical reactors, valve internals — improved chemical resistance

Decorative stainless

Architectural stainless features — mirror cosmetic finish

High-vacuum hardware

UHV chamber components — reduced outgassing, cleaner surface

04 · When not to use it

Not suitable for:

Every process has its limits. Being honest about where Electropolishing isn\'t the right answer saves time and money.

Non-stainless materials — aluminum, titanium, carbon steel not electropolishable
Parts where 10–25 µm material removal would exceed tolerance budget
Parts with narrow blind cavities — electrolyte circulation difficult
Very high volume where cost of electropolishing exceeds marginal benefit
Parts requiring specific surface textures (anti-slip) — electropolishing produces smooth only

FAQ

Electropolishing questions.

Electropolish: better corrosion resistance (removes smeared surface material), no embedded abrasive contamination, deburrs automatically, accesses complex internal surfaces. Mechanical polish: faster for small areas, doesn't remove material (no dimensional change), lower cost per part for simple geometry. For pharmaceutical, medical, and corrosion-critical applications, electropolish is dramatically better. For cost-sensitive decorative, mechanical polish is often adequate.

Yes — typically 10–25 µm (0.01–0.025 mm) of material removed per surface. Plan machined dimensions accordingly: for a bore that must be Ø10.0 mm finished after electropolish, machine to Ø9.98 mm before electropolishing. We can advise on specific allowances based on part geometry during DFM review.

Yes — and this is one of the best applications for electropolishing. Weld heat-affected zones and weld metal have different surface chemistry than parent metal. Mechanical polishing cannot equalize this. Electropolishing removes the surface layer of both parent and weld metal uniformly, leaving a homogeneous passive layer across the entire welded assembly. Standard for pharmaceutical and food welded vessels.

ASME BPE (Bioprocessing Equipment) specifies Ra 0.38 µm maximum surface finish for pharmaceutical process contact surfaces. Mechanical polish can achieve this but electropolishing is preferred for: better cleanability, reduced biofilm adhesion, easier sanitization. Certified-compliant BPE electropolishing available through our qualified partner with full documentation.

Typical electropolishing lead time: 3–5 business days after parts arrive at finishing station. This is an added step to overall manufacturing — plan for total lead time including CNC/fabrication plus finishing. Documentation (surface finish verification, process records) adds 1–2 days for pharma orders. Rush available with 2 days.

Small parts (under 100 mm): $3–10 per part. Medium parts (100–500 mm): $10–40 per part. Large vessels or long tubing: priced per surface area — typically $100–300 per m² of surface. Cost justifies itself for pharmaceutical and medical applications through reduced cleaning/validation overhead. For general stainless applications, electropolishing premium may or may not be justified depending on requirements.