Ah btw just an idea; you might want to try converting to black and white. Colour isn't really an element in this shot anyway and if you do it well, you may be able to really bring out the detail in the metal and the clouds in the background.
EDIT: I've just downloaded the image and had a go at converting it to BW. Hope you don't mind
You've obviously added quite a bit of sharpening already, so my conversion looks a little weird.
Oh and if you don't mind sending me the original (full size, unsharpened, hopefully RAW? ;P) file i'd really like to see what I can do with it