Official Answer
Answer
Passivation is a critical chemical process (per ASTM A967) that removes free iron from the surface of 17-7PH wave springs, enhancing the protective chromium-oxide layer. In medical instruments, this prevents localized pitting and 'tea-staining' during repeated autoclave sterilization cycles. The process involves immersion in nitric or citric acid baths. For 17-7PH, passivation is performed after the CH900 heat treatment to ensure any surface contaminants introduced during the coiling or aging process are removed. This ensures biocompatibility and long-term reliability in sensitive surgical environments.
