RapidDirect Passivation Services

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.