I'm working on boxing the frame rails of my current scratch-built project and am using some 10 ga that came from my grandfather. He's been gone a while and I can't tell if the steel is oxydizing stainless or galvanized. Years ago he said it was stainless and used some of the sheet when he grafted a camaro stub onto his '52 Chev pickup but I would like to be sure before I start welding in my pieces (since welding galvanized is toxic!) Here's a pic of a leftover piece to show what it looks like now. Any thoughts?