Found a $2 anode the size of a thumbnail on the leg of a rig in Port Fourchon
Honestly I almost walked right past it until the deck hand pointed at the pitting behind it, and that little thing had been eating the whole leg for a year. Anybody else catch a sacrificial anode in the weirdest spot? What was it eating?
That pitting behind the anode is the real story, once that zinc is half gone the current starts jumping to whatever bare steel is closest and it eats a crater fast. I pulled a 3 pound anode off a riser clamp last spring that was doing the same thing, looked fine from the boat side but the back was hollowed out like a sponge. First thing I'd do is grab a silver/silver chloride half cell or even a cheap multimeter and check the potential on that leg before you just bolt a new one on. If it's reading lower than -850 mV you got a bigger problem than one anode, could be a stray current from a nearby dock or a bonding issue. Also take a wire brush to the pit and hit it with a caliper, if it's more than 10 percent of wall thickness that leg needs an inspection, not just a new zinc. The deck hand probably saved you a diver bill down the road.