Once rust gets started it doesn't tend to stop. It's a chemical reaction. The metal is oxidizing. If it's only on the outside, or on the grain hopper, probably no biggie. If it's on the rollers, kind of a biggie. Most likely though, if you can see it on the outside, then it's definitely on the inside where the rollers attach to the base and the handle, and that's a huge problem. You might go to brew in a few weeks and find your rollers seized from the rust. If you can take it apart do it now, and get it thoroughly dry, and then take some sand paper or a wire brush or maybe some rust remover to it and get that stuff off there. It's that or possibly buy a new mill some day soon.