Why not surgical implant steel?
Steel should only be considered for short term wear in fully healed piercings only. Nickel (13 to15% by volume) is dissolved in the F138 alloy to make it non-magnetic and resistant to corrosion. This alloy is supposed to trap nickel and other irritants under a layer of chrome (chromium oxide, which is susceptible to corrosion by chlorine, such as the salt in perspiration) where it releases allergens and toxins very slowly. As ions of the metal diffuse into skin, the tissue reacts to protect itself and granulates thick scar tissue around the offending item to wall it off, like a splinter.