The passivation process is a method of improving the corrosion resistance of stainless steel parts by removing ferrous contaminants like free iron from their surface, 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 nor make it visibly brighter.
By comparison, electropolishing removes burrs, heat tint and oxide scale and makes parts made from a wider variety of stainless steel and other metal alloys 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.