There are a few metals that are not very reflective, but are closer to dull gray. They are usually very soft and oxidise very quickly to form a thin, matted coat on the surface. Some of the most common examples are iron (not steel) and lead.
Try using a lighter gray color, or even a mix of colors (blended with a dirtmap), for the Diffuse.
There is an interesting relationship between Bump and Reflections for this type of metal. The areas that are scuffed or scratched are more reflective and polished than the rest. So what is black in the Bump map, should be lighter in Reflection and Gloss slots. This is easy to do if you are using a mix map with a dirtmap texture to define the mix colors.
Diffuse
Reflect
Gloss
Bump
In this example, we are using the Bump map, combined with a normal map, to give the material more uneven feel. The normal map can be swapped out to something different, or you can get rid of it altogther if the goal is a very smooth surface.
Lead is very similar, but the diffuse color is a lighter gray and the reflections are a bit stronger and lighter.
Adjusting the scratches and aging is as simple as changing the mix amount to a different bitmap. (Tip: instance them so you only have to change one.)
