If you treated the edge of the knife with the Sentry Solutions Tuf-Cloth that should have come with your knife, it shouldn't rust simply from humidity. In any case, certainly sharpening would remove the rust. However, if it is just a light surface rust, you can try removing it with a pencil eraser, then treat with the Tuf-Cloth. If you live in very high humidity conditions and it continues to be a problem you may want to try Marine Tuf-Cloth.