What ASME BPE finish should a bioreactor have?

Product-contact surfaces in bioreactors are most often specified to SF4 (15 µin Ra max, mechanically polished and electropolished), with SF5 or SF6 used where the process is less sensitive. The drawing or owner's specification governs.

Does electropolishing reduce biofilm?

It reduces the places biofilm can start. An electropolished surface has far fewer microscopic crevices than a mechanically polished one, so it holds less residue and cleans more completely. It does not replace a validated cleaning cycle.

Do you provide Ra readings with the parts?

Yes. Profilometer Ra readings mapped to location ship with finish-specified work, along with a certificate of conformance. Chromium-to-iron ratio results confirming passivation are available on request.

Can large bioprocess vessels be finished on-site?

Yes. Vessels that cannot ship are mechanically polished, electropolished or passivated in place by our field crews in the Houston area and along the Gulf Coast.

Electropolishing and Passivation for Bioprocess and Biotech Equipment

Electropolished 316L sanitary component for bioprocess equipment at Harrison Electropolishing

Reviewed by Tom Harrison, member of the ASME BPE Surface Finish Subcommittee · Updated October 2026

The short answer: Bioprocess equipment lives or dies on cleanability. Cell culture, fermentation and purification systems are specified to ASME BPE surface-finish designations because a lower-Ra, electropolished 316L surface sheds fewer particles, anchors less biofilm and validates faster. Harrison electropolishes and passivates bioreactors, vessels, hygienic tubing and skid components to SF4–SF6, documents the Ra, and ships with a certificate of conformance.

What we finish for biotech customers

Bioreactors and fermenters. Interior mechanical polishing and electropolishing of vessels, jackets excluded, including nozzles, baffles and agitator shafts.

Buffer, media and hold vessels. Finished to the designation on the drawing, with Ra mapped by location.

Hygienic tubing and transfer panels. Orbital-welded 316L spools, manifolds and transfer panels electropolished per ASTM B912 or passivated per ASTM A967 before installation.

Skid-mounted systems and stainless hardware on single-use platforms. Stainless totes, frames and connection hardware around single-use assemblies are passivated or electropolished so they do not become the contamination source in an otherwise disposable train.

ASME BPE surface finish, in brief

Designation	Finish	Ra max (µin)	Ra max (µm)
SF1	Mechanically polished	20	0.51
SF2	Mechanically polished	25	0.64
SF3	Mechanically polished	30	0.76
SF4	Mechanically polished + electropolished	15	0.38
SF5	Mechanically polished + electropolished	20	0.51
SF6	Mechanically polished + electropolished	25	0.64

Tom Harrison, our founder, serves on the ASME BPE Surface Finish Subcommittee that maintains these designations and has served on the board of ISPE. If a drawing calls out a finish by old "grit" language instead of a designation, we will help translate it before quoting. More in what is ASME BPE and Ra vs RMS.

Why electropolishing is the biotech standard

Electropolishing dissolves the microscopic peaks left by mechanical polishing and leaves a chromium-enriched, featureless surface. For a bioprocess train that means less product and protein adhesion, faster CIP with less chemistry, fewer sites for biofilm, and a surface that stays passive through repeated SIP cycles. It is also non-particulating, which matters downstream of filtration.

Representative project

A biologics contract manufacturer commissioning a new upstream suite needed a set of 316L bioreactors, media-prep vessels and the connecting hygienic tubing finished to SF4 and documented for its validation package. Harrison mechanically polished and electropolished the vessel interiors, electropolished the tubing and transfer-panel components in batches, passivated and verified each item, and delivered profilometer Ra readings keyed to the vessel drawings with a certificate of conformance. Validation proceeded without surface-finish findings.

Request a biotech quote

Send drawings or a component list with the alloy, the ASME BPE designation or Ra target, and your delivery date. We quote within one business day; expedited service is available and lead times vary with shop load.

Request a Quote · Call 800-245-5707

More to Know

Frequently Asked Questions

What ASME BPE finish should a bioreactor have?

Product-contact surfaces in bioreactors are most often specified to SF4 (15 µin Ra max, mechanically polished and electropolished), with SF5 or SF6 used where the process is less sensitive. The drawing or owner's specification governs.

Does electropolishing reduce biofilm?

It reduces the places biofilm can start. An electropolished surface has far fewer microscopic crevices than a mechanically polished one, so it holds less residue and cleans more completely. It does not replace a validated cleaning cycle.

Can you finish stainless hardware used with single-use systems?

Yes. Stainless totes, frames, connection hardware and transfer panels around single-use assemblies are passivated or electropolished so they meet the same cleanliness expectations as the disposable components.

Do you provide Ra readings with the parts?

Yes. Profilometer Ra readings mapped to location ship with finish-specified work, along with a certificate of conformance. Chromium-to-iron ratio results confirming passivation are available on request.

Can large bioprocess vessels be finished on-site?

Yes. Vessels that cannot ship are mechanically polished, electropolished or passivated in place by our field crews in the Houston area and along the Gulf Coast.

Request a Quote

800-245-5707

Electropolishing

Harrison Electropolishing, the Leading Electropolishing, Passivation, Oxygen Cleaning & Mechanical Polishing Company World Wide.

Electropolishing is an electrochemical process by which surface material is removed by anodic dissolution. Electropolishing removes surface material, beginning with the high points within the microscopic surface texture. By removing these points, the electropolishing process will improve the surface finish of a metal such as stainless steel, nickel, and Hastelloy, leaving a smoother and more reflective surface. Common parts and components electropolished include tanks, piping, fittings, rods, discs, large parts & surfaces, and more.