Originally Posted by alystra
Asked the question of the manufacturers when I ordered chains for my ketch many years ago. The chains are put in a 'tumbler', or revolving mesh drum, which is dipped in the molten zinc and rotated after removal until the coating hardens.
I had it re-galvanised in a place in Glasgow. They didn't have a tumbler, just hit it with hammers till all the links freed up. Not as good though as there were bits that weren't covered - however it didn't go rusty. I presume the surrounding zinc was protection enough.
The galvanising should protect the uncoated areas, because the zinc is a less noble material, the parent material becomes the cathode and the zinc works as the anode, the water is the electrolight, completing the corrosion circuit.
With bare parent material exposed this will excelerate giving a shorter life to the chain.
Sorry to be a saddo, but working with cathodic protection is part of my job.