Stainless Steel Drawing Notes
How to specify passivation and when it is required
Passivation is one of the most common stainless steel finish notes, but it is also one of the easiest to under-specify.
Short answer
Specify passivation when stainless corrosion resistance or cleanliness depends on it
Passivation is required when a drawing, purchase order, customer requirement, quality plan, or industry standard requires it. It is also commonly specified when stainless steel parts will be exposed to corrosion risk or when machining, fabrication, welding, or handling could leave contaminant iron on the surface.
A good drawing note does more than say "passivate." It tells the supplier which standard applies, which treatment family is allowed, how effectiveness is verified, which areas are excluded, and whether records are required.
What passivation does
Removes surface contamination
For stainless steel parts, passivation is commonly specified to remove free iron and other surface contaminants so the stainless surface can maintain corrosion resistance.
When it is required
When the drawing, purchase order, standard, customer, or application requires it
It is especially common for stainless parts exposed to corrosion, sanitary service, medical use, aerospace requirements, or contamination-sensitive environments.
What it is not
Not a coating
Passivation does not hide scratches, improve roughness, add paint-like protection, or replace cleaning, descaling, electropolishing, or material selection.
Best drawing note
Standard + treatment + test + records
A useful note names the governing standard, allowed treatment family, required verification test, masked/excluded areas, and certificate or record requirement.
Requirement guide
When is passivation required?
Passivation is not automatically required for every stainless part. It becomes necessary when the service condition, customer requirement, contamination risk, or governing specification makes a clean passive stainless surface part of the design requirement.
| Scenario | Required? | Review guidance |
|---|---|---|
| The drawing, customer specification, purchase order, or quality plan says passivate | Yes | Treat passivation as required. Clarify the standard, treatment, verification test, sampling plan, and documentation if the requirement is incomplete. |
| Machined stainless steel will be exposed to humidity, washdown, salt, chemicals, or outdoor service | Usually | Passivation is commonly specified because machining, handling, or tooling can leave contaminant iron on the surface. |
| Medical, food, pharmaceutical, clean-process, aerospace, or nuclear stainless components | Often | These applications often require high cleanliness and corrosion resistance. Verify the governing customer or regulatory requirement. |
| Stainless weldments with heat tint, scale, or heavy oxide | Passivation alone may not be enough | Descaling, pickling, mechanical cleaning, or other preparation may be required before passivation can be effective. |
| Decorative stainless part with no corrosion or cleanliness requirement | Maybe not | If the finish is cosmetic only, brushing, polishing, bead blasting, or electropolishing may be more relevant than a passivation callout. |
| Carbon steel, alloy steel, aluminum, or plated steel part | No, not stainless passivation | Use the appropriate coating, plating, conversion coating, oil, paint, anodize, or corrosion protection process for that material. |
Drawing notes
What to include when specifying passivation
The exact note depends on your company, supplier, customer, material, and application. These are the fields reviewers should expect to see or intentionally leave to the supplier.
Governing standard
ASTM A967/A967M, ASTM A380/A380M, and SAE AMS2700 do different jobs. Name the one the supplier must meet.
Passivate per ASTM A967/A967M.
Treatment family
If the process matters, specify nitric, citric, electrochemical, or an AMS2700 method/type. If it does not matter, allow supplier selection under the standard.
Citric acid treatment acceptable.
Precleaning and descaling
Passivation cannot fix heavy scale, weld heat tint, embedded abrasive, oil, or trapped chips by itself.
Remove scale, oil, chips, and free iron before passivation.
Verification test
A passivation note without an acceptance test can leave inspection unclear.
Verify per copper sulfate test unless otherwise approved.
Masked or excluded areas
Identification marks, threaded inserts, assemblies, sensitive surfaces, or non-stainless components may need special handling.
Protect installed bearings and non-stainless inserts from process chemicals.
Certification and records
Critical parts often need lot traceability, process records, and test results.
Certificate of conformance required with passivation lot and test method.
Example notes
Example passivation drawing notes
Treat these as starting points for review. Your released drawing should follow your governing standards and quality system.
General stainless machined part
Passivate stainless steel parts per ASTM A967/A967M. Supplier may select an appropriate nitric or citric treatment for the alloy. Verify effectiveness per the selected standard test method. Certificate of conformance required.
Use when: The supplier is qualified and you do not need to control the exact acid chemistry.
Aerospace or controlled-process part
Passivate corrosion-resistant steel per SAE AMS2700. Method, type, acceptance test, sampling plan, and records per drawing or purchase order requirements.
Use when: Customer, aerospace, defense, or quality requirements point to AMS2700.
Welded stainless assembly
Clean, descale or pickle as required, then passivate stainless steel surfaces per ASTM A380/A380M and ASTM A967/A967M. Remove heat tint and contaminant iron from weld and heat-affected areas. Verify per approved free-iron test.
Use when: Weld heat tint, oxide scale, fabrication residue, or installed-system cleaning matters.
Minimal note that needs review
Passivate all stainless parts.
Use when: This is a weak note. Redline it to add a standard, acceptance test, exclusions, and documentation requirements.
Review checklist
Common passivation mistakes to catch in review
Many passivation problems are drawing problems: missing standards, vague notes, unprotected assemblies, or expectations that passivation will do more than it can.
- Calling out passivation on carbon steel or aluminum when another corrosion-protection process is needed.
- Expecting passivation to remove weld scale, heat tint, oil, embedded abrasive, or burrs without a cleaning or descaling requirement.
- Leaving the standard unspecified, which forces the supplier to guess between ASTM A967, ASTM A380, AMS2700, or legacy requirements.
- Failing to define the verification test or certificate requirement for critical parts.
- Applying a blanket passivation note to assemblies with non-stainless inserts, bearings, electronics, coatings, or trapped cavities.
- Treating passivation as a cosmetic finish. It does not make a part polished, smooth, or scratch-free.
PDF Engineer workflow
Redline passivation requirements directly on the drawing
Use PDF Engineer to mark the exact passivated surfaces, flag vague blanket notes, add supplier questions, and attach test or certificate requirements to the finish note before the drawing goes out for quote or release.
- Confirm the material is a passivation-appropriate stainless or corrosion-resistant steel.
- Check whether passivation is contractually required by the drawing, PO, customer spec, industry standard, or quality plan.
- Identify whether the part only needs passivation, or whether cleaning, descaling, pickling, or electropolishing is also required.
- Mark the surfaces that need passivation and any areas that must be protected or excluded.
- Verify that the passivation standard, treatment options, test method, acceptance criteria, sampling, and records are clear.
- Review dimensional features, threads, assemblies, and trapped cavities for process risk.
- Use PDF Engineer redlines to attach passivation questions directly to the drawing faces, notes, and supplier requirements.
Bottom line
Passivation is required when stainless cleanliness is a requirement, not a habit
Specify it clearly when contamination, corrosion, cleanliness, customer requirements, or standards make it necessary.
Do not use it casually as a cosmetic finish, coating, descaling step, or substitute for proper stainless material selection.
Review the note for standard, treatment, acceptance test, exclusions, and records before release.
FAQ
Passivation questions
When is passivation required?
Passivation is required when the drawing, purchase order, customer specification, industry standard, or quality plan requires it. It is often specified for stainless parts exposed to corrosive environments, contamination-sensitive service, food or pharmaceutical use, medical applications, aerospace requirements, or other high-cleanliness applications.
Is passivation always required for stainless steel?
No. Stainless steel can form a passive surface naturally when it is clean and exposed to oxygen, but passivation is often specified to remove contaminant iron and help ensure a chemically clean surface after machining, fabrication, or handling.
What standard should I use to specify passivation?
ASTM A967/A967M is commonly used for chemical passivation treatments for stainless steel parts. ASTM A380/A380M is broader and covers cleaning, descaling, pickling, and passivation practices. SAE AMS2700 is common in aerospace and other controlled corrosion-resistant steel applications.
Does passivation add thickness?
Passivation is not a plating or paint process. It is normally specified to remove contaminant iron and support a clean passive stainless surface, not to add a dimensional coating.
Can passivation remove weld discoloration?
Not reliably by itself. Weld heat tint and scale may require descaling, pickling, mechanical cleaning, or other preparation before passivation. The drawing or process specification should make that explicit.
Sources
Standards references
Passivation standards change over time. Confirm the exact revision required by your drawing, customer, purchase order, and quality system.
- ASTM A967/A967M-25
ASTM describes A967/A967M as covering chemical passivation treatments for stainless steel parts, including nitric acid, citric acid, electrochemical treatment, rinsing, visual requirements, and qualitative tests for effectiveness.
- ASTM A380/A380M-25
ASTM describes A380/A380M as a practice covering cleaning, descaling, pickling, and passivation recommendations and precautions for stainless steel parts, assemblies, equipment, and systems.
- SAE AMS2700
SAE describes AMS2700 as defining engineering requirements for a process intended to remove free iron or other less noble contaminants from corrosion-resistant steel parts.
- ASTM A01.14 standards listing
ASTM's A01.14 committee listing identifies active corrosion-testing standards including A967/A967M-25 and A380/A380M-25.
- DLA ASSIST AMS2700 listing
DLA ASSIST lists SAE AMS2700 as active for passivation of corrosion-resistant steels, with adoption and review information for defense-standardization contexts.