Passivation
钝化处理
Chemical passivation for stainless steel that removes free iron and maximises the protective chromium oxide layer.
Passivation is a chemical treatment for stainless steel that removes free iron contamination, manganese sulfide inclusions, and other surface impurities introduced during machining, forming, and handling. The process restores and enhances the naturally forming chromium oxide passive layer, maximising corrosion resistance.
At Active Treatment, we perform passivation using nitric acid or citric acid baths depending on the alloy and application. Citric acid passivation is preferred for medical, food processing, and pharmaceutical applications where contamination risks must be minimised.
Post-passivation testing (copper sulfate test, high humidity test) is available on request.
Key Benefits
- Removes free iron and surface contaminants
- Maximises native chromium oxide passive layer
- Prevents pitting and crevice corrosion
- Citric acid option for medical/food applications
- Meets ASTM A967 and AMS 2700 specifications
Specifications
| Standard | ASTM A967, AMS 2700, ASTM A380 |
|---|---|
| Process options | Nitric acid, citric acid |
| Applicable alloys | 300-series, 400-series stainless, precipitation hardening grades |
| Testing available | Copper sulfate, water immersion, high humidity |
Frequently Asked Questions
Why does stainless steel need passivation if it's already 'stainless'?
Machining, grinding, and handling introduce free iron particles and surface damage that compromise the natural passive layer. Without passivation, these contaminated areas can initiate rust and pitting corrosion — even on 316L stainless steel.
What is the difference between nitric acid and citric acid passivation?
Nitric acid is the traditional passivation method, effective for most grades. Citric acid is a safer, more environmentally friendly alternative with equivalent or better results for most 300-series alloys. Citric acid is preferred for medical devices and food equipment due to lower toxicity.
Does passivation change the dimensions or appearance of my parts?
No. Passivation removes a submicron surface layer of contaminants. There is no measurable dimensional change and the surface finish is not altered.
How do I know if my parts need passivation?
Parts requiring passivation typically include: freshly machined stainless steel, components assembled with mild steel tooling, parts stored or transported with ferrous metals, or any stainless application where rust spots or contamination have appeared.
Can you passivate assembled components?
Yes, with care. Assemblies with dissimilar metals (e.g., titanium fasteners in stainless housings) require special handling. Please inform us of all materials present so we select a compatible passivation process.
Request a Quote
Contact Active Treatment Pte Ltd in Singapore for Passivation. Call +65 6352 9846 or email activetreatment88@yahoo.com.sg.