Alternatives to protecting steel armor?

[Gaius Colletti]

Thank you all for the replies, Ballistol had me at "Protects metals and LEATHER" though, and I already ordered a bottle. Thank you Medicus Matt, although I found the bit about wool soaked with lanolin oil kept in scabbards very interesting, and I might try that someday, but that the fact that ballistol leaves a slippery surface and binds with whatever you put it on instead of just rubbing off an evaporating like mineral oil does tipped the scale.

Thank you all again, and please continue the discussion about appropriate time period solutions or modern ones