I did a lot of research
on this recently prior to painting my new saildrive lower legs. The consensus is that a few coats of epoxy barrier coat is a must. Some schools of thought say that the leg can then be painted with a normal copper-based anti-fouling
and people who have done this have reported no ill-effects, the thinking is that as long as the copper based paint does not come into contact with the aluminum
leg then there will be no corrosion
. However, erring on the side of caution and not wanting to ruin an expensive drive, I went with the other school
of thought which advocates using Trilux 33 anti-fouling
which is designed for aluminum and can be applied in thick coats, unlike the aluminum anti-fouling that you buy in spray cans.