It won't hurt it. We put little tubes of copper in the sea strainers of the boat's air conditioning systems to keep the barnacle growth down inside the cooling coils of the condensing units. And the best saltwater bottom paint is made with copper dust. Copper and saltwater...no problem.
The salt will wreck the copper. It kills lots of parasite in saltwater environments hence the use in systems described above. You will get a lot of patina on the surfaces and eventual failure if you use it enough. However unless you brew multiple times a week you probably won't see it fail for a few years, but it will fail sooner than with just water.