Hi Guys,
Just my 2 cents..................
Zinc plates have been welded to the hulls of ships to prevent damage to the steel hull and brass screws by galvanic reaction.....
The more active metal is sacrificed to protect the less active.....
Zinc is a less active metal and unable to protect aluminum....
To prevent galvanic damage to aluminum a magnesium anode should be used....
For additional info I will post a link speaks to galvanic action...
http://www.performancemetals.com/anodes/AnodeFAQs.shtml
Bob