What is Passivation in Surface Treatment?
Passive treatment is a chemical process that enhances the corrosion resistance of stainless steel and other alloys by forming a thin, transparent oxide layer on the surface.
Unlike coatings or plating, passivation does not change the part’s appearance or dimensions but provides a clean, protective finish that improves durability and performance.
This process is widely used in industries such as medical, aerospace, and precision engineering, where high reliability and corrosion resistance are critical.
At TONZA, we provide professional passive treatment services tailored to your material and application requirements.
With our advanced equipment and expertise in precision surface finishing, we ensure your parts achieve optimal corrosion resistance, cleanliness, and long-term stability.
Main Feature
Passive treatment, also called passivation, is a chemical process that enhances the natural corrosion resistance of stainless steel and alloys. By forming a thin, protective oxide layer on the surface, it removes impurities and prevents rust without changing the material’s appearance or dimensions. This makes it an ideal finishing solution for industries requiring durability, cleanliness, and long-term performance.
Advantages
- Enhanced Corrosion Resistance – Creates a stable oxide layer that protects stainless steel and alloys from rust and chemical attack.
- No Dimensional Change – Since it’s a chemical reaction, the process does not alter part dimensions or tolerances.
- Improved Cleanliness – Removes contaminants, free iron, and impurities from the surface, leaving a smooth, clean finish.
- Extended Service Life – Increases durability and reliability of parts in harsh environments.
- Cost-Effective Protection – Provides long-term corrosion resistance without adding coatings or plating.
- Environmentally Friendly – Uses chemical treatment rather than adding extra materials, reducing waste compared to coatings.
Disadvantages
- Material Limitation – Works best on stainless steels and some alloys; not suitable for all metals.
- Surface Condition Dependent – Effectiveness relies on proper cleaning and preparation; poor surface condition reduces performance.
- No Mechanical Strength Improvement – Passivation only improves corrosion resistance, not hardness or wear resistance.
- Chemical Handling Risks – Involves acids that require strict safety measures during processing.
- Periodic Maintenance Needed – In certain applications, parts may require re-passivation over time.
Design Considerations for Passivation Parts
Our CNC equipment deliver tight specifications that conform to industry requirements, securing consistent accuracy and perfect piece fit.
Material Selection
Ensure the part is made from stainless steel or alloys that respond well to passivation; not all metals benefit equally.
Surface Finish
Smooth, uniform surfaces enhance passivation results; rough or porous surfaces may trap contaminants.
Contamination Control
Avoid introducing free iron or foreign metals during machining, as these can hinder effective passivation.
Tolerances & Dimensions
Passivation does not change part dimensions, but design must allow for complete solution access to all surfaces.
Complex Geometries
Deep holes, blind cavities, and tight corners may limit chemical flow; designs should minimize hard-to-reach areas.
Post-Machining Cleaning
Parts should be free from oils, lubricants, and machining residues before passivation to ensure optimal protection.
Welded Assemblies
Welds and heat-affected zones may require additional treatment or polishing before passivation for uniform results.
End-Use Environment
Consider the operating conditions (marine, medical, aerospace, etc.) to determine the appropriate level of passivation.
Re-Passivation Needs
In harsh environments, plan for potential re-passivation during the part’s service life.
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FAQ about Passivation
For a clearer understanding of what we offer, here are FAQs on our Passivation process.
Frequently Asked Questions
All-in-One questions for Customer
Passivation is most effective for stainless steels (300 and 400 series), precipitation-hardened stainless alloys, and some nickel alloys. Other metals such as aluminum or carbon steel do not benefit from the process.
No, passivation does not alter dimensions or add a coating. The process is chemical in nature, leaving parts with the same size, shape, and finish but with enhanced corrosion resistance.
Passivation works by dissolving surface contaminants and enriching the chromium content at the surface, which forms a stable, invisible oxide film that resists rust and chemical attack.
Industries such as medical device manufacturing, aerospace, automotive, food processing, and precision engineering rely on passivated parts for their durability, cleanliness, and resistance to harsh environments.
Common standards include ASTM A967, ASTM A380, and AMS 2700. These guidelines define the proper procedures, chemical baths, and testing methods to ensure high-quality passivation.
Yes, but welds may contain heat tint or oxide layers that require pre-treatment such as pickling or polishing before passivation to achieve uniform protection.
In normal environments, a single passivation is sufficient for long-term performance. However, in highly corrosive settings such as marine or chemical industries, parts may require periodic re-passivation.
Passivation does not improve mechanical strength, hardness, or wear resistance. It also requires precise cleaning and is only effective on corrosion-resistant alloys like stainless steel.