wouldn't zinc make the metal rust faster? i read somewhere on here about putting a zinc block on the underside of the truck to attract some type of chemical so the rust eats it away before anything else. said it was a technique used on boats.
sacrificial anode
It's a softer material that's supposed to degrade instead of your pontoons, hull, transom, drive, outboard or any other metal parts that may be in contact with the water. It'd be nearly pointless to use on a truck unless you're constantly driving through creeks though
Here's a link to better describe it
http://en.wikipedia.org/wiki/Sacrificial_anode
