Zinc! Wha..?

If you put metal in water, water's gonna eat that metal.  This is a problem for boaters, so they solve that problem through a thing called sacrificial anodes, which are made of zinc.  Zinc attracts electrolysis more than any other metal, so just place those anodes around your important metal stuff, and the anode will get eaten first.  Problem solved... as long as you replace your zincs on a regular basis.

Here's a photo of a sacrificial zinc after it's been in fresh water for a couple years, and a new one on the left.  The brand name is "Martyr." Perfect.

"Thank God I still live in a world of telephones, car batteries, handguns, and many things made of zinc." Simpsons, episode 8F16