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RapidDirect Passivation Services
RapidDirect offers quality passivation services and can guarantee excellent surface finishes for metal parts with intricate features and complex geometry.
What's Passivation?
Passivation is a chemical process that enhances the corrosion resistance of metals such as stainless steel by removing free iron and other contaminants from their surface and creating a passive oxide layer called the passivated finish.
Chemical passivation is different from coating or plating. The process of passivation involves placing the stainless-steel part in passivation tanks containing dilute acid solutions such as nitric or citric acid.
The choice of solution can determine the name of the passivation. For example, nitric acid passivation uses nitric acid, while nitric acid and sodium dichromate passivation contains nitric acid and sodium dichromate.
Passivation Specifications
| Applicable Materials | Cosmetic Availability | Visual Appearance |
|---|---|---|
| Stainless Steel, Copper, Brass | N/A | No significant visual change exists, but the metal surface becomes more inert and less prone to oxidation. |
Advantages
- Reduced susceptibility to corrosion resistance
- Removes surface contaminants and impurities, which improves part’s cleanliness
- It prevents discoloration, staining, or rust formation of the stainless-steel part.
Notes
- It does not increase the wear resistance of the part surface.
Applications of Passivation
Aerospace Industry: Aircraft components such as fasteners, fittings, and brackets are passivated to prevent corrosion and maintain structural integrity in harsh environments.
Automotive Industry: Stainless steel exhaust systems, fasteners, and fuel lines are passivated to improve corrosion resistance, ensuring longevity and reliability under extreme conditions.
Medical Devices: Surgical instruments, implants, and hospital equipment undergo passivation to enhance corrosion resistance, ensuring they remain sterile and durable in critical healthcare environments.
Electronics: Connectors, enclosures, and precision parts are passivated to protect against corrosion, ensuring reliable performance and longevity in sensitive electronic applications
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FAQs
Stainless steel passivation is a chemical process that enhances the corrosion resistance of stainless steel parts. It involves cleaning the stainless steel to remove contaminants such as free iron and other surface impurities. After cleaning, the parts are treated with an acid solution, typically nitric or citric acid, which promotes the formation of a thin, transparent passive oxide layer on the surface. This oxide layer protects the stainless steel from further oxidation and corrosion, significantly improving its durability and performance in corrosive environments.
Yes, stainless steel naturally passivates in specific environments by forming a thin, protective oxide layer when exposed to oxygen. This layer enhances corrosion resistance and protects the material from environmental damage. However, to ensure optimal and consistent passivation, especially in demanding applications, chemical passivation treatments using acid like nitric or citric acid is the best due to the accelerated formation of the passive oxide layer.
You can know if passivation is successful by using visual inspection, chemical testing, and corrosion resistance testing.
Using visual inspection means checking for a clean, uniform surface without discoloration, staining, or visible contaminants. Chemical testing involves tests like ferroxyl test to detect iron deposits. The ferroxyl test detects iron contamination by applying a solution that turns blue in the presence of iron.
Lastly, corrosion resistance testing involves using salt spray or humidity tests to assess the part’s resistance to corrosion. A successfully passivated part will show no signs of rust or corrosion after the test.
Electropolishing and electropickling are surface treatment processes similar to passivation but involving different mechanisms. Electropolishing removes surface imperfections and enhances the surface finish, while electropickling removes surface contaminants and scale.
Nitric acid passivation can cause oxidation of the stainless steel surface due to its strong oxidizing properties. In contrast, citric acid passivation does not induce oxidation as its passivation is milder and more environmentally friendly while still effectively removing contaminants and promoting the formation of the passive oxide layer.
The correct term for the process is “passivation.” Passivation is a chemical process used to enhance the corrosion resistance of stainless steel by removing contaminants and promoting the formation of a passive oxide layer on the surface.
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