So I lived in SF for six years, and it was absolutely the dog piss that did it.
I know this because outside my apartment were two metal utility poles. One, right it outside the door, was the dog piss spot. The other, 20 feet away, was not.
Guess which one corroded and had to be replaced after three years? It was the one that absolutely reeked of dog piss right outside the door.
Also what “salt water mist?” The Castro is inland, and it’s not like there are huge waves blasting clouds of mist into the air.