Basically you need to do a google on galvanic action and look at the galvanic chart. Each metal reacts differently to electrons, with the least noble of the two corroding or sacraficing itself. The further apart on the galvanic chart the metals are the greater the reaction will be. For practical purposes it looks like if you put copper and cast iron together (touching each other) in a salt water bath, the cast iron would rust quite quickly.



There's the science lesson for today. LOL