Stainless Steel Passivation: Standards
A chemical clean that puts the stainless surface back the way the mill intended — required for medical and food-contact parts.
Request a quoteWhat actually happens to the part
The part is immersed in an acid solution that dissolves free iron contamination left by machining, leaving a chromium-rich passive oxide layer that resists corrosion.
| Parameter | Value |
|---|---|
| ASTM A967 | Standard passivation practice for stainless |
| ISO 16061 | Passivation of stainless steel for medical use |
| Citric acid | Non-chemical, food and medical friendly |
| Nitric acid | Standard, more aggressive, needs more handling |
| Pickling | Removes visible scale, not a substitute |
| Surface roughness | No change |
| Typical lead time added | Add 2–4 working days |
What this finish does to your tolerances
This is where most prototype surprises come from. A finish is not decoration — it moves dimensions, and the drawing has to account for it.
Effectively none — the process removes a molecular layer, not material dimension. This is why it is specified on medical parts where any dimensional change would be a problem.
Suitable for
- SS 304
- SS 316L
- Titanium (grade 2 and 5)
Not suitable for
- Aluminium and copper — pickling attacks them
- Parts with iron contamination from carbon steel tooling that has not been cleaned
What engineers ask about Stainless Steel Passivation: Standards
Is passivation the same as pickling?
No. Pickling removes mill scale and visible oxidation with a stronger acid. Passivation is a gentler clean that removes free iron and restores the passive layer. A part can be pickled and still need passivation.
Do medical parts always need passivation?
If the part is stainless and touches tissue or fluid, passivation is usually specified, often under ISO 16061 rather than ASTM A967. We confirm which standard the drawing calls for before quoting.