i have a becker bk7 utility knife that rusted up on me after my last camping trip. not the whole blade, just the honed edge. the rest of the blade is coated, rather good i'd say, because it is still in awesome shape and i chopped the crap out of wood with it while camping...
anyway, in my situation, all i need to do is sharpen the blade up (to get the rusty metal off the edge, then coat it with militec-1 or hoppe's gun oil, then slide is back in the sheath (which is lined with plactic casing) and store inside a closet away from moisture.
hope this helps, and good luck!