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If a coating wore off, then that was probably a plastic coating over the steel. Stainless steel contains chromium and nickel within the steel. Those metals form
by Tagbert 5y ago
If a coating wore off, then that was probably a plastic coating over the steel. Stainless steel contains chromium and nickel within the steel. Those metals form a hard protective surface that blocks oxygen. If that surface were scratched, the underlying metals would reform the protective surface upon exposure to oxygen.
- 1MachineElf 5y agoEither way, it's also possible that the coating on the bottle's rim was wore down by saliva. For stainless steel, research has been done for certain grades like 316 for dental applications, but it's possible other grades are not as resistant.