There are other finishes to make a firearm corrosion resistant. Get it Parkerized with manganese phosphate, coat it with enamel like Para does, or you can even gold plate it like a Deagle (ick).
Here are example of Blue/Case/Nickel, just for your edification.
And I have to say, after handling a model 40... I'd prefer it, maybe, even with the grip safety and the old grip, to the alloy 642, and lock-cursed 640.
I do like the look of case hardening, But not on that pistol with a blued barrel.