Passivation is a widely used chemical process that enhances the corrosion resistance of stainless steel by removing free iron from its surface, allowing a protective oxide layer to form. Industries such as semiconductor, biopharmaceutical, and medical rely on this process to ensure material purity and long-term durability.
SilcoTek's new state-of-the-art passivation line.
According to Able Electropolishing, most stainless steels, particularly 200 and 300 series alloys, respond well to passivation. The process effectively removes surface contaminants, improving corrosion resistance.
At SilcoTek, we utilize citric acid passivation in compliance with ASTM A967 standards, preparing stainless steel surfaces for our high-performance coatings. This step ensures that our coatings adhere properly and function optimally in challenging environments.
| Sample | Cr/Fe Total | CrOx/FeOx | Estimated Oxide Thickness (nm) |
| 1 | 1.9 | 3.2 | 2.4 |
Able Electropolishing notes that certain materials, such as free-machining steels, may not respond well to standard passivation due to their unique compositions. These materials may require electropolishing or other alternative treatments to achieve the desired corrosion resistance and cleanliness.
In addition to material incompatibilities, some complex geometries are not suitable for passivation. Parts with blind holes or intricate designs may trap acid or rinsing solutions. However, for certain geometries, we are able to secure parts to a fixture that would allow the acid to drain properly. Our team is trained and able to develop custom tooling to efficiently process customer parts.
While passivation can be an essential process for stainless steel, SilcoTek takes material performance a step further by applying CVD coatings that significantly enhance corrosion resistance, chemical inertness, and overall longevity.
When paired with SilcoTek's Dursan coating technology, the benefit of passivation is much more evident, as illustrated in Figure 1. Passivation helped to slow down the corrosion progression over time and reduce the corrosion rate by over half during the first month of exposure. The passivated coupons also showed less pitting in comparison to the unpassivated coupons at the end of the test 32 day (Figure 1 right).
Figure 1 (left): corrosion rate progression of Dursan-coated 316 SS in 5% HCl with and without passivation over 32 days, showing the benefit of passivation and (right): visual comparison showing less pitting for the passivated samples at the end of the test.
By integrating passivation with advanced coatings, SilcoTek provides a comprehensive surface treatment solution that enhances both corrosion resistance and overall component performance. This approach ensures that critical parts used in demanding applications maintain their integrity and functionality for extended periods.
Whether you have questions on our passivation or coating processes, other applications, or wondering if your parts can be passivated, our team would love to talk to you! Please reach out to our knowledgeable team for more information!