Just wanted to pass this along. I always had a can of wd40 in the greenhouse and used it to keep cutters, etc. from sticking. Someone told me that wd40 causes metal to rust, no wonder they are all rusty. Now I use a silicon spray instead, I had no idea wd40 caused rust on metal.

Never heard that one, been using it since my navy days over 40 years ago.

I've been told by many gun buffs that WD-40 tends to attract and hold water, promoting corrosion if used for long-term storage..

The WD-40 website doesn't seem to agree - they claim that it prevents corrosion. Maybe the difference lies in using it for long-term storage vs. removing some water today.

I stopped using it when I found a thumbprint rusted into some blueing that had been "protected" with WD-40.

I've heard people who were positive on both sides of the WD-40 question.

It does tend to get thick and gummy and dirty even more than a thin layer of real oil does.

Now I only use WD-40 to break up rust, unfreeze a bolt, or displace water ... then I wipe it off, clean with a solvent, and relace it with real oil or silicon-based grease. I don't know what I'll do when my tube of RIG runs empty - it isn't made any more.

Some people suggest using Johnson Wax to put a hard, slick, rust-proof coating on metal. However, on a garden tool, it would be abraded opff rather quickly in use.
I love the idea of a bucket of sand plus oil, but get the metal clean (and maybe dry) before plunging it or you'll fill the oil with dirt and water.