Official Answer
Answer
Passivation (ASTM A967) is a critical post-manufacturing process for stainless steel rings. During coiling and handling, particles of 'tramp iron' from the tooling can become embedded in the surface of the ring. These particles act as initiation sites for corrosion (pitting). Passivation involves immersing the rings in a nitric or citric acid bath which dissolves the free iron and enhances the formation of a thin, protective chromium-oxide layer. For medical or aerospace components, passivation ensures that the ring remains 'stainless' and prevents premature failure due to localized galvanic corrosion cell formation.
