WD-40 will kind of prevent rust, for a short time. Remember it is basically kerosene and it evaporates fairly quickly. Its main mission in life is to disperse water based machining coolants to prevent flash rusting between operations and before finishing. We use a ton of it in the machine shop for this use and it works great. Its also a great cleaner! It is NOT a lubricant although it works well for tapping threads in Brass.
Long term storage you will do better with a wax layer, especially on wood working tools where oil could stain the work. For chisels and the like Carnauba wax does pretty well.
The Boeshield is more or less a wax that is dissolved in a carrier solvent. Spray it on and let the solvent evaporate and buff off the excess. There was an in-depth test on a cast iron saw table done in a humidity chamber a while back. I think it was Fine Woodworking Magizine perhaps. They applied a bunch of products to squares on the table then blew moist air on it. The WD-40 held up for about an hour, IIRC the test was terminated before the Boeshield area showed rust!
The interesting thing comparing WD-40 and Boeshield is that one was developed for Convair and the other by Boeing.
The other thing Boeshield works great for is lubricating roller chains, like on a bicycle.
Another great product is LPS-3 heavy duty rust preventer. I don't like it as much as it seems to be gloppy and doesn't cover as well. We use a lot of Boeshield. At least in a machine shop we aren't so concerned with oil mucking up the workpieces. We only have to worry when running certain plastics like Teflon and porous phenolics that the customer wants uncontaminated.
http://boeshield.com/
