hi jaimedc and thank you.
for the orange metal material i used a tri shader material composed by different materials controlled by mixer.
darker orange (corrosion, dust,...) is opaque and with a littele bump effect on border and the lighter is shining and flat (consumed and thin paint);scratches are only shining and bumped.
for the green material i used a quad shader material similar to the previous because i have created two different type of metal.
here the orange material example.
some Duncan views: