Frederick, you are in the US, on line. Shop around
I've read several authors say that chain is not worth the expense of re-galvanizing. Just buy new chain. By the time you figure in freight both ways and then the shop time to acid wash rusty chain and then hot galvanizing, well you get the idea. Just sell your old stuff. It'll work for a mooring,,,or something. And that foof-can stuff won't adhere well to a moving chain, even if you could reach everywhere between the links. Save it for the anchor.