I have a 525 with the silver nitride finish. You must keep it lightly oiled like the rest of the gun. I let mine go for a week or so in a very humid condition. A tiny bit of rust showed up on the left side of the receiver. About the width of a pencil lead and 1/4” long. It came off easily with a few light strokes of steel wool, but it left a bit of discoloration similar to faded bluing. It’s not really a problem unless you are a perfectionist, which I’m not, but just the same, keep it oiled and out of humidity for storage. I like a silver finish much better than a blued finish and would buy one again without hesitation.