I have the same problem often.Our humidity here is so high that any ferrous machined surface exposed to the atmosphere is likely to develop surface rusting in days and will progress from there.I am currently using a spray product I picked up at Lowes, I believe marketed by Dupont--they have 2 kinds packaged nearly alike 1 is a dry lubricant containing Teflon and 1 is a wet lubricant containing the same.Label says leaves a wax like film that lubes and protects from rust.I am using the dry type on seldom used tools and metal surfaces and so far I like what I see.Wipes off easily with a petroleum solvent or brake cleaner.I have used a similar product by LPS and many rattle can paint racks have a similar product.DON'T use WD 40.It attracts moisture and in the end makes things worse.
For some serious rust protection take a look at some products by Sanchem Inc. they have some powerful stuff.
Anybody heard of "cosmoline"?
