darkening wheels on postear locos

[Anonymous]

Is there a qay to darken the iron wheels on postwar locos without painting them? My engines are in excellent condition, but the wheels are fading. How can I blacken them up to look better?
Thanks

[FJ and G]

I'm thinking gun blue. Probably would work on scintered iron.

Here's a nice piece

http://www.gunsandammomag.com/techside/blue_0515/