The passivation process is a method of improving the corrosion resistance of stainless steel parts by removing ferrous contaminants like free iron that are embedded in their surfaces, restoring them to their original corrosion specifications.
To passivate stainless steel parts, they must be submerged in a chemical solution of citric acid or nitric acid for a certain period of time and at a certain temperature. This removes foreign matter like free iron from the surface, but does not remove the heat tint or oxide scale that may be left behind by welding or heat treating. The passivation process improves corrosion resistance and leaves a clean finish, but ultimately does not change a part’s appearance or make it visibly brighter.
While you can passivate stainless steel to improve its corrosion resistance, not all grades are suited for this process, and some parts may require additional cleaning operations beforehand.