Hi all.. I am in the last stage of my new project, "black box for cars". I have designed it's operation somewhat similar to the black box using in aircrafts. The system almost works good enough and some final modifications are there. I have approached the custom sheet metal fabricators Bayview Metals for making the box. But when I reached there I have little bit confused about the metal to be chosen for my black box. What type of metals is perfect for such systems? What all things I have to notice while I make it as a finished product? Please reply me.