What is passivation or aluminium conversion coating?
Stainless-steel passivation addresses contamination on a chemically clean stainless surface and supports its passive condition. Aluminium conversion treatment uses substrate-specific chemistry to create a surface selected for corrosion, paint-adhesion or electrical-contact requirements. Neither treatment should be specified only by a colour name.
Key specifications
Process references and example callouts are identified below. CHIHENG confirms the accepted material, dimensions and treatment requirements in the part quotation.
| Parameter | Reference / what to specify |
|---|---|
| Material / route | Stainless steel: passivation; aluminium: compatible conversion chemistry. State the exact grade. |
| Specification | ASTM A967/A967M-25 for stainless passivation; provide the aluminium conversion specification separately. |
| Film thickness | No shared µm range applies to these two treatment families. Use the selected treatment’s acceptance requirements. |
| Tolerance | Not a dimensional correction process; identify fitted and masked features. |
| Colour / contact | Appearance and electrical performance depend on chemistry, not just colour. |
| Size / records | Review immersion and drainage from CAD; agree verification and required treatment records. |
Technical references: ASTM A967/A967M-25
Applications
Industrial equipment
Stainless fittings and fasteners with specified passivation.
Electronics
Aluminium housings with defined conversion and contact requirements.
Fluid-handling equipment
Stainless components with customer-defined contamination acceptance criteria.
Working with CHIHENG
A direct conversation with our team, from your first drawing to delivery.
A reply within 24 hours
Send us your drawing and questions. Our team will reply within 24 hours and help you work out the next step.
An experienced engineering team
Talk through materials, tolerances and finishing with engineers who understand how your part will be made.
Machining equipment
We use our machining equipment and practical manufacturing experience to turn your drawings into finished parts.
Competitive worldwide shipping
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Process steps
- Identify the substrate and the material-specific treatment specification.
- Clean the surface and address scale, oil or contamination with the specified preparation.
- Apply the selected chemical treatment, then complete the required rinsing and drying.
- Verify the agreed requirements and protect the surface from handling contamination.
Passivation or aluminium conversion coating vs Anodising
| Comparison point | Passivation or aluminium conversion coating | Anodising |
|---|---|---|
| Substrate | Different routes for stainless steel and aluminium | Aluminium in this service |
| Function | Chemistry-specific passivation or conversion requirements | A defined oxide coating for protection or appearance |
| Dimensions | Acceptance follows the chosen chemical treatment | Oxide growth must be considered in finished fits |
| Electrical contact | Select the conversion chemistry and required test | Oxide is generally insulating; contact faces need review |
Choosing the right treatment
- Start with the material grade. Stainless steel passivation and aluminium conversion coating need different treatment specifications.
- Include the required chemistry, restrictions and acceptance tests, rather than colour alone.
- Tell us about cleanliness, handling and packaging requirements so the treated surfaces stay protected.
FAQ
Is stainless passivation the same as aluminium chromate conversion?
No. They are different treatments for different substrates. Identify the base metal and the required specification when requesting a quote. Stainless passivation and aluminium conversion should not share an unspecified process note. State the material, governing specification and required function so the correct route can be reviewed.
Will this hide machining marks?
These chemical treatments should not be specified as a way to remove tool marks. Define any cosmetic surface preparation separately. Identify any required contact performance and verification method. Do not infer electrical suitability from the surface colour or substitute a visually similar chemistry without approval.
Can I specify a particular chemistry?
Yes. Include the exact treatment requirement and any restrictions on chemistry or documentation. Availability and compliance must be confirmed for the order. Request the treatment designation, batch reference and agreed verification records. Specify the contract standard and chemistry restrictions with the drawing before the component is quoted.
Does ASTM A967 apply to aluminium?
ASTM A967/A967M covers chemical passivation treatments for stainless-steel parts. It is not an aluminium conversion-coating specification. For aluminium, provide the governing treatment requirement, chemistry restrictions and any electrical-contact or paint-adhesion criteria. The correct substrate and specification must be resolved before a treatment can be selected or accepted.
Does passivation remove roughness or machining marks?
Passivation is not a polishing operation or a substitute for the correct cleaning and descaling route. Oil, scale and contamination require appropriate preparation. If appearance, burr removal or roughness matters, specify those requirements separately so machining, mechanical surface preparation and chemical treatment are reviewed as distinct operations on the drawing.
