There are a lot of products out there designed to protect bare metal from rust. Reportedly a product called Boeshield is best, but is expensive. Fluid Film is another popular product. There is a thread on hobby-machinist.com that discuses this subject and provides some home-made remedies. https://www.hobby-machinist.com/threads/misting-oil-to-protect-machine-surfaces-in-a-damp-environment.81051/ 


Brownells did a study of rust preventing products. You can look at it here.

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=12616