Hej cramerx,
take a look at the attached image.
Juraj was pointing to this method of getting the average refect color from your ref.-image.
You crop the image to the "metal-borders" and then calculate the average color.
This way you get pretty close to the real image reflect color.
What I think about your last attempt is:
1. I think you have to model the hammered parts of the ref-image (pipe etc.).
2. Take a better look at the "striped-pointed" bump parts of the material. There you will have to use a special map, not just any dirt map.
Hope it helps + all the best
Nico