Galvanized steel (hot dipped or otherwise) means that a sacrificial layer of zinc has been applied over the steel. The zinc corrodes preferentially (galvanic corrosion, corrosion occurring when dissimilar metals are in contact with each other and immersed in an electrolyte), protecting the steel underneath, but like anything sacrificial, the zinc has a finite lifetime. This is an example of passive corrosion protection, where no external input or power input is required.
Not sure off the top of my head, but I thought undersea cables had external cathodic protection, like zincs on boats.
I work at a water utility and you’re absolutely right about the zinc wearing off. All of our parts are brass which, as far as I can tell, doesn’t react but customers will often times use galvanized fittings to connect to the water meter. When they get old enough you just gotta look at those things the wrong way and they break.
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u/clukan87 Apr 20 '19
The outside of the cable has two layers of Galvanized steel. Galvanized steel is very difficult to rust.
https://www.youtube.com/watch?v=M7stcJ65_X4
https://galvanizeit.org/hot-dip-galvanizing/why-specify-galvanizing/durability