I think what you actually have going on there is what is called electrolysis or galvanic corrosion. It occurs when you submerse metals into a liquid, and usually the less noble metal gets eaten up. This is exactly what you have in boats that stay in the water, where underwater parts begin to get eroded away. That is why boats use sacrificial zincs, because the zinc will take the hit rather than the shafts, rudders, etc.

You might even have some stray electrical currents accelerating the process. This might sound strange, but I think they sell zincs for cooling systems to protect parts like aluminum.

Don