Paul Industries carries out passivation, electropolishing coordination and surface verification for New Hampshire medical device and precision manufacturers. Device surface work is governed by a different standard from equipment passivation and for a different reason. On a process vessel the passive film protects the metal. On an implant it also controls what the metal releases into a patient, which is why ASTM F86 exists separately from ASTM A967 and why specifying the wrong one is a genuine error rather than a paperwork preference.
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Two standards, and they are not interchangeable
ASTM A967 covers passivation of stainless steel parts generally, and it is the correct reference for process equipment, piping and vessels. ASTM F86 addresses surface preparation and marking of metallic surgical implants, and it exists because an implant has requirements a pressure vessel does not.
The difference is what the passive film is being asked to do. On equipment, it prevents corrosion and keeps the metal intact. On an implant, it does that and also forms the interface between the device and living tissue for years, which means it governs the rate at which metal ions migrate out of the device and into the patient. For stainless implants that means nickel and chromium; for nickel-titanium alloys it means nickel specifically, and the concern is well enough established that surface condition is a design input rather than a finishing detail.
The practical consequences for a New Hampshire manufacturer are three.
Specify F86 on implantable components and mean it. A supplier quoting a passivation process to A967 is quoting the right process for the wrong application. They will often be broadly similar in chemistry, and the acceptance criteria, documentation and intent are not.
Do not assume the alloy standard is enough. The material specification and the surface specification are separate. A part in correctly certified implant-grade stainless with an inadequately prepared surface is not a compliant part.
Separate device work from equipment work physically. The tank, the tooling and the handling used for implant components should not be the ones used for process equipment. Cross-contamination in a passivation bath is a real route, and the economics of sharing a tank look better than they are.
Nitinol, which behaves unlike anything else in the shop
Nickel-titanium alloy is used widely in stents, guidewires and other devices for its superelasticity and shape memory, and it is covered by ASTM F2063. Its surface presents a problem that stainless does not.
The alloy is roughly half nickel. What makes it acceptable in the body is that its surface, properly prepared, is a titanium-rich oxide rather than an exposed alloy face, and that oxide is what limits nickel release. A poorly prepared nitinol surface can present far more nickel to tissue than a well prepared one made from identical material, which puts surface processing at the center of the device’s biocompatibility rather than at its periphery.
Two features of the material make that harder than it sounds.
Thermal processing leaves heavy oxide. Nitinol is heat treated to set its transformation behavior, and that heat treatment leaves a thick, nickel-rich surface layer that must be removed rather than merely cleaned. Removing it is a material removal operation, and it changes dimensions on components whose tolerances are already fine.
The geometries are unforgiving. Fine wire, laser-cut tubing with intricate strut patterns, complex formed shapes. Achieving a uniform surface across those is a process control problem, and the edges left by laser cutting are precisely where an incomplete process shows.
Electropolishing is the usual answer because it does several things at once: it removes material preferentially from peaks and edges, which smooths the cut faces that matter most; it removes the nickel-rich layer; and it leaves a titanium-enriched oxide. Verification then has to reflect the concern, which means surface composition and ion release behavior rather than a roughness reading alone.
| Heating load | Per treatment | Per 20 treatments |
|---|---|---|
| 30 kW | $38.90 | $778 |
| 60 kW | $77.81 | $1,556 |
| 120 kW | $155.62 | $3,112 |
At 16.21 cents per kilowatt-hour, 1.99 times the national average (EIA, 2024), heated process baths are a real running cost in New Hampshire, which favors ambient-temperature chemistries where the application permits them and makes bath insulation and lid discipline worth more than they appear.
Verification, and the number that is not sufficient on its own
Surface roughness is the figure most often specified and it describes amplitude rather than character. As set out on our South Carolina surface finish page, two surfaces at identical roughness can behave quite differently depending on how the deviation is distributed. On a device that matters for a further reason: a recess or a re-entrant feature that a roughness trace never enters can retain cleaning chemistry, processing residue or bioburden, and it will not appear in the measurement at all.
The verification that actually reflects the requirement therefore has several parts.
Passivation effectiveness by a method appropriate to the part and the material, with the method recorded rather than merely the result.
Surface composition where the concern is ion release, because that is the property in question and roughness is only a proxy for it.
Cleanliness in terms of residue and particulate, which is the subject of our New Hampshire precision cleaning page and is a separate test from surface condition.
Visual examination at magnification of the features that matter, particularly laser-cut edges and any re-entrant geometry, because that is where an incomplete process is visible and a trace is not.
We carry out passivation to ASTM A967 for equipment and to ASTM F86 for implant components, coordinate electropolishing and verify what comes back rather than accepting a certificate, handle heat tint removal on fabricated assemblies, and advise on separating device processing from equipment processing where a client is currently sharing facilities.
Standards referenced: ASTM F86 · ASTM A967 · EIA electricity price data · ASME BPE · 21 CFR 820 · ISO 13485
Frequently asked questions
Do you provide device surface finishing services in New Hampshire?
Yes, across Manchester, Nashua, Salem, Portsmouth and statewide: passivation to ASTM A967 for equipment and ASTM F86 for implant components, electropolishing coordination and verification, heat tint removal, and advice on separating device from equipment processing.
What is the difference between ASTM A967 and ASTM F86?
A967 covers passivation of stainless parts generally and is right for process equipment. F86 addresses surface preparation of metallic surgical implants, because an implant’s passive film also governs the rate at which metal ions migrate into a patient over years, which a pressure vessel’s film does not have to do.
Can we specify A967 on an implant component?
It is the right process for the wrong application. The chemistry is often broadly similar, and the acceptance criteria, documentation and intent differ. A supplier quoting A967 for implantable work has not understood the requirement, and that is worth catching at the purchase order rather than at audit.
Is the material certificate enough?
No. Material specification and surface specification are separate requirements. A part made from correctly certified implant-grade stainless with an inadequately prepared surface is not a compliant part, and the two are frequently assumed to be one thing.
Why is nitinol a special case?
Because the alloy is roughly half nickel, and what makes it acceptable in the body is a titanium-rich surface oxide rather than an exposed alloy face. A poorly prepared surface can present far more nickel to tissue than a well prepared one made from identical material, so surface processing is central to biocompatibility.
What does heat treatment do to nitinol surfaces?
It leaves a thick nickel-rich oxide layer that has to be removed rather than cleaned. Removal is a material removal operation, which changes dimensions on components whose tolerances are already fine, so it belongs in the process plan rather than being treated as a finishing step.
Why electropolish rather than just passivate?
Because it does three things at once: removes material preferentially from peaks and edges, which smooths laser-cut faces; removes the nickel-rich layer; and leaves a titanium-enriched oxide. Passivation alone does not remove material and so cannot address the first two.
Should device and equipment processing share a tank?
No. Tanks, tooling and handling used for implant components should be separate from those used for process equipment, because cross-contamination in a bath is a real route. The economics of sharing look better than they are once the consequence is considered.
Is surface roughness a sufficient specification?
No. It describes amplitude rather than character, and on a device a recess or re-entrant feature that a trace never enters can retain chemistry, residue or bioburden without appearing in the measurement. Verification should also cover passivation effectiveness, surface composition where ion release matters, cleanliness, and visual examination at magnification.
How do I get a quote for New Hampshire device finishing work?
Use the form on this page or call 201-450-8280. Useful inputs are the alloy and whether the component is implantable, the geometry including any laser-cut or re-entrant features, the surface specification and how it is verified, and whether device and equipment processing currently share facilities.
How is a device passivation process controlled for consistency?
By fixing the chemistry concentration, temperature, time and rinse parameters within validated ranges, monitoring the bath and replacing it on a schedule set by loading, and recording each lot's parameters. Process control turns a chemical treatment into a manufacturing step.
How is a device passivation process validated?
As a manufacturing process under 21 CFR 820 and ISO 13485, with the process parameters defined, the equipment qualified and the outcome verified against the device's requirements, including corrosion testing and surface analysis where the design history file calls for them.
What tests verify an implant surface?
Free iron tests, corrosion tests such as those referenced in the device's standards, surface analysis by X-ray photoelectron spectroscopy for chromium-to-iron ratio where required, and cleanliness testing. The test set is defined in the design history file.
How are cobalt-chromium implant alloys passivated?
With the same acid families as stainless but under a validated procedure for the alloy, because cobalt-chromium forms its own chromium oxide film and responds differently to nitric and citric chemistry; the process is qualified with corrosion testing on the alloy rather than transferred from stainless. Each implant alloy carries its own validated recipe.
How is a nitinol component's surface oxide managed?
By controlling the thermal processing that forms the oxide, removing the thick oxide from shape-setting by mechanical or chemical means, and then passivating or electropolishing to leave a thin, uniform titanium oxide layer. The oxide's thickness and composition determine corrosion resistance and nickel release.
How does surface treatment relate to biocompatibility testing?
Cytotoxicity, sensitisation and other tests under ISO 10993 are run on the finished, passivated surface, so a change in passivation chemistry, cleaning or electropolishing is a change to the tested article and may require retesting. The surface process is locked once the biological testing is done.
How are device parts protected from contamination after passivation?
By handling with clean tools and gloves, packaging in clean materials, and separating the passivated parts from unfinished work and from the plant's general environment. A passivated surface picks up iron and organics as readily as an unpassivated one if it is handled carelessly.
How is device passivation documented?
With a device history record entry for each lot: chemistry lot, parameters, verification results and operator, tied to the validated process. The record supports the device's release.
What about titanium implant surfaces?
Titanium alloys form stable oxides and are cleaned and treated to remove contamination and control the surface, often with etching or anodising, under the device's validated process. Stainless chemistry is not used on them.
How is laser marking related to surface work?
Marking alters the surface locally, can create oxide and heat-affected zones, and can affect corrosion resistance and cleanliness. Marking is validated as a surface process and passivation may follow it.
What surface analysis confirms an implant's passive layer?
X-ray photoelectron spectroscopy or Auger analysis measuring the chromium-to-iron ratio and oxide thickness at the surface, used during process validation and on failure investigations, with production lots verified by simpler tests. The analysis proves the film exists as specified, which a copper sulfate test cannot.
What role does cleanliness play before passivation?
Passivation on a contaminated surface treats the contamination, not the metal, so cleaning validation precedes passivation validation. Machining fluids and polishing compounds have to be removed and verified gone.
How is spent chemistry from a device line handled?
Neutralised and discharged under permit, with segregation from equipment processing waste, and with records that support the facility's environmental compliance. Small volumes from device lines are often collected rather than discharged.
Do you also passivate the plant's process equipment?
Yes, to ASTM A967 for vessels, piping and fixtures, as a separate activity from device processing, on its own equipment and chemistry. The two are kept apart.
What is the commonest device surface specification error?
Referencing A967 on an implant drawing because it was on the equipment drawings, and discovering at audit that the device standard was F86. The specification is corrected at design.
Marking, which is surface work that arrives disguised as printing
ASTM F86 addresses surface preparation and marking of surgical implants together, and the pairing is deliberate. Marking a device is a surface operation, and it undoes surface preparation unless it is planned as part of the same process.
Devices need identifying: unique device identification, lot and serial numbers, orientation marks, sizing. On an implant that marking has to survive sterilization, remain legible for the life of the device, and not create a site where corrosion or ion release begins. Those requirements conflict with each other more than people expect.
Laser marking is the usual method and it is thermal. It works by locally heating the surface, which means it alters the oxide layer exactly where it is applied and can leave heat-affected material beneath. A mark applied after passivation has locally removed the thing the passivation created.
Depth is a trade against integrity. A deeper mark is more legible and survives handling better; it is also a recess that can retain cleaning chemistry and processing residue, and a stress concentration if it sits somewhere that matters mechanically. Marking location on a loaded component is a design decision rather than a labelling one.
Mechanical marking introduces its own contamination. Stamping and engraving deform the surface and can embed material from the tool, which on a device is the same free iron problem that afflicts process equipment, with higher consequences.
The sequencing that resolves most of this is straightforward once stated: mark first, then finish. Apply the mark, then carry out the cleaning and passivation, so the final surface treatment covers the marked area as well as everything else. Doing it the other way round, which is the intuitive order because marking feels like the last step, leaves the most thermally disturbed area on the part as the only area that was never treated.
Where marking genuinely must come last, for example where it carries data not available earlier, the mark needs its own local treatment afterwards, and the validation has to demonstrate that the treatment reached it.
The verification question worth asking of any marked implant is simply whether anyone has examined the marked area specifically, at magnification, rather than examining the part generally. It is the smallest area on the component and the most likely to be the one that fails.
Device surface specification questions in New Hampshire?
Tell us the alloy, whether the part is implantable, and what your current surface specification says. If it names A967 on an implant, that is where to start. Call 201-450-8280 or use the form below.