get a jar of naval jelly from the hardware store and a cheap paintbrush. paint
a coating of the stuff on the garden tool and let it sit for 10 to 15 minutes.
then, rinse it off and rub the garden tool dry with a soft cloth or paper
towel. THEN, rub on some WD-40. work on one tool at a time. works like a charm!
the garden tools will look almost brand-new!

pat