Official Answer
Answer
Passivation (per ASTM A967) is a chemical treatment in nitric or citric acid that removes 'tramp' iron and other surface contaminants from the stainless steel. This process enhances the formation of a thin, protective chromium-oxide layer. Without passivation, microscopic iron particles from the manufacturing tooling can embed in the ring surface and cause 'bloom' or localized pitting in corrosive environments. For 316 Stainless Steel, which contains molybdenum for better chloride resistance, passivation is critical for subsea applications to prevent crevice corrosion within the groove where stagnant water can accumulate.
