After stainless steel part has been manufactured, an important additional step needs to be taken in order to make the part rust-resistant. This vital next step is called passivation which keeps the metal from corroding.
What is Passivation?
Passivation is a process which enhances the corrosion resistance of metal components. During the process, parts are cleaned, then immersed in an acidic passivating bath.
Why is it Done?
After a stainless steel part has been made, it needs to undergo the process of passivation in order to improve the appearance and functionality of the part. The process of manufacturing the part can leave grease and other substances on the part’s surface. These substances can form iron which slows the formation of the oxide film that is needed in order to protect the stainless steel part from corrosion. After passivation, the surface of the metal is clear of imperfections and ready for priming and painting.
How is it Done?
The process of passivation happens in two steps. The first step is to thoroughly clean the part from any substances introduced to its surface in the manufacturing process. This step is vital to the passivation process since contamination can cause damage to the metal.
The second step is for the steel to be immersed in a passivating bath. Three different approaches can be used for the acidic bath:
- Nitric acid passivation
- Nitric acid with sodium dichromate passivation
- Citric acid passivation
The passivating bath works to remove iron particles on the surface of the metal and grow a protective film over the part. The protective film is a passive oxide layer that gives the metal a rust-resistant quality that improves the appearance and functionality of the part. After being tested to pass testing requirements, the part is finished with the passivation process and ready for use. Typically, this testing can be done for salt spray, water immersion, and humidity.
Interested in how a functional finish could improve the performance and appearance of your product? Passivation is the best way to ensure longer lasting parts that are resistant to corrosives. Call ECF for more information.