re: Hardware, Brass I think

My choice would be a piano hinge made from stainless steel. These are very strong and will take the abuse of a tool box. You will need to get one from a marine store because the ones at the box stores have a steel rod to connect the parts and not a S.S. rod.
An other thing I remember from my youth in Denmark, was the fishermen putting galvanized fittings in BLO (boiled linseed oil) for several weeks and then letting it air dry. The metal turned dark gray/black in a workman style tradition. Not unattractive by any means.