I have my students use Johnson’s paste wax on all metals to help
minimize oxidation. I have recently seen it at both Ace Hardware and
Lowe’s. Other paste waxes work as well, such as Trewax. Renaissance
wax is, perhaps, the best as it is a micro crystalline wax
formulated for preservation. However, it is about $25 for what would
cost about $3 Johnson’s.
Also, it is important that the surface of the metal be completely
clean before waxing, as any fingerprints or other oils on the metal
before waxing will still oxidize.