Zinc question

[OBT]

I’m installing aN underwater stainless steel structure on my boat. It is not connected to any other metal. Is it necessary to attach a zinc to it?

[Sailmonkey]

An anode will still protect the metal from corrosion. The anode is sacrificial compared to the metal it’s attached to.

[SVHarmonie]

A simplistic answer would be no, since it is not connected to any other metals, but that would be incomplete--and wrong. Stainless steels of all flavors can be quite widely separated on the galvanic scale depending on the local environment, the exact alloy, weld history, and a bunch of other variables.

If this was a single piece of cast stainless with no fasteners, welds, bent pieces, crevices, you could skip the zinc. I am sure whatever it is you are proposing is not such a thing, so a zinc will help, and never hurt.