When using aluminum, always use one wire size larger than what is specified
for copper wire. I've seen aluminum used in telephone company ground fields
for years, I don't think the corrosion is any worse than copper. Always use
a no-oxide "grease" when connecting aluminum to a different metal, like
copper or a lot of corrosion will occur. Do a "Google" search on the
subject and you'll probably find all the information you want.