The manual for my dishwasher says to refill salt just before running a wash cycle, because if any grains of salt spill onto the stainless steel interior it will corrode. If it runs right away, no issue because the salt is quickly dissolved, diluted, and flushed.
So then I realized when I cook pasta I heavily salt the water (following the advice that pasta water should taste as salty as the ocean). But what happens when I leave that highly salty brine in a pot, sometimes for a couple days to reuse it? Does that risk corroding the pots?
Even stainless steel will corrode, and salt especially will speed up the process. Solid salt is much worse than salt water, because the concentration of solid salt is 100% vs a fraction of a percent for pasta water. Regardless, leaving salt water sitting in your pot for days on end is definitely going to make corrosion occur faster, although by how much I can’t say.
Although, I will say that needing to buy even one additional pot might offset any environmental benefit from reusing your pasta water. Industrial manufacturing uses a ton of water, so if your goal is to preserve it, you’re likely better off just washing & drying your pot out between uses so that it lasts longer.
I could always transfer it to glass or plastic to protect the pot but I guess laziness was the original motivator. Salt is cheap enough that I’ll probably just toss it going forward.