OOoo ... I don't know about WD 40.

I did a test on it out in the garage years ago and on bare steel it seemed to actually attract rust. A cousin once said the same thing, that WD 40 contributed to causing rusting on his admittedly well used and abused and neglected Winchester Model 12 shotgun.

It's for certain that, as a rust preventative, WD 40 falls short.