Originally Posted by martini
Apparently the extra life doesn't warrant the extra cost. The zinc soon wears off with the links chafing against each other all the time.
I dived a mooring for a yacht owning friend a few years ago who'd used black chain. 12mm chain was down to about 2mm thickness and ready to snap in the next big blow on some links on the bottom.
I used 16mm galvanized into a mooring block and six years on it's still showing no signs of corrosion. You're probably right chafing removes zinc from where it chafes but you may misunderstand how the galvanizing works. It's not like powdercoating or paint where a hermetic seal over the bare metal is required. The chafed area between links is still close to zinc plating which will continue to be sacrificial and reduce corrosion on even bare metal on the same link.
Unless it's really easy to inspect and replace I'd use galvanized. At the very least I'd use a length of galvanized into the concrete mooring if that's what you'll have in each corner or you could have to replace the blocks too if the chain is cast into them and rusts out.