Spotted this through the railing on the north side of the Walkway Over the Hudson:
I’m not sure what it’s bonding to the bridge structure, but the corrosion where the braid touches the I-beam suggests an electrical potential drives the reaction. There’s stout bonding braid connecting all the railing sections together, but this braid wanders off below the decking and seems too casual / flimsy for lightning protection.
The rivets date back to the late 1800s. I suspect that bolt won’t last nearly as long…
The Smell of Molten Projects in the Morning 