Most wire coat hangers do have a galvanised zinc coating as does barbed wire, its that grey oxidised looking stuff.
Its easy enough to remove in a fire, you will be sure its gone if the wire will rust over its surface if you leave out in the rain etc.
Zinc is definitly a toxic heavy metal, so dont breathe the fumes, welders get a complaint called metal fume fever from welding galvanised.
Im a huge fan of coat hanger wire, its very versatile, and is easy to get. as is old barbed wire, which as Mike Ameling points out is stiffer due to its higher carbon content.