The map is gonna work well, but think about where the rust and scratches will most likely be on moving pieces. Right now, it's too even across the entire surface. The scratches are also too straight, too perfect, and probably a bit too deep. Also, when you finish your scratch bump, use the same map in your spec, so you get shiny spec hits where the scratches have cut through the surface. 
http://us.123rf.com/400wm/400/400/g...chain-vertical-blur-background-copy-space.jpg
Even though it's a bad resolution image, you can see here where the rust sows up more often. Also check out the angled swirling scratches and marks, that follow the way the piece moves. Reference like this will work out real good!
http://us.123rf.com/400wm/400/400/g...chain-vertical-blur-background-copy-space.jpg
Even though it's a bad resolution image, you can see here where the rust sows up more often. Also check out the angled swirling scratches and marks, that follow the way the piece moves. Reference like this will work out real good!