If you’re gonna mount a Strombos 5-chime under your vehicle, then powder coat the manifold. The Bu-ell locomotive horn’s bracket is welded-together steel, and will quickly rust. However, the bells and power chambers are brass which is impervious to salt, hence why is perfect for marine usage. Powder coat is perfect for under-vehicle installation, my powder coat company also powder coats auto chassis for the same reason.
To be fair, it is under-vehicle, but it’s a closed-off spare tire well with holes cut in the side which are then covered with a mesh screen. This is a Camry after-all. I’ll still coat the manifold for safety, but my UPs went through many rainstorms and salty, wet roads after snowstorms and they barely have spots on them.