Originally Posted by bradedup
yeah my brass cored KMs and syrians do this....just brass oxidizing.
Exactly, it's not rust per-say, but oxidation. Like TE mentioned, scrubbing it with a wire brush, and baking soda / lemon juice will do the trick to take off the oxidation / tarnish. I used a brillo pad on the outside of my dual tone KM to remove the tarnish. worked like a dream.