To clarify, my bus bar of aluminum is not battery interconnects, it is a DC distribution bus kind of like what Chris described for his system, only smaller. For batteries I would want the least active metal I could find for the interconnects, or lead itself. Aluminum, because of its rapid corrosion in acids and its much larger potential difference with lead, would not be among my first choices, in fact it would be one of my last. I think lead tinned copper interconnects would be my first choice for battery interconnects for batteries with lead terminals. I've seen brass marine terminals partly eaten away by corrosion, and I would expect aluminum to fare much worse in that application. I do use Aluminum interconnects on my ultra capacitor banks, but, the terminals of those capacitors are of aluminum alloy. Again, with greased connections, I have had no problems with those as well. Unless there is a reason to do otherwise, I would use the metals with the closest electrical oxidation potential for junctions to avoid galvanic corrosion. I heard somewhere that a general rule of thumb is not to join metals together in exposed joints if the oxidation potential between them was greater than .5 volts, and it seems like a basically reasonable guide. Junctions of metal where the oxidation potentials exceed that would have to have protection from the environment in order to avoid galvanic corrosion because any of the more noble metal oxidized would likely be reduced in favor of oxidation of the more active metal at the junction if a galvanic cell were to form, such as condensation, rain, or such. This is the idea behind sacrificial anodes, often made of magnesium or aluminum, which are used on pipelines and in some hot water tanks. Most Junctions with Aluminum would require protection from the environment. In my case I used anti-oxidation grease made for such a purpose.
Here are the different potentials of some common metals relative to the oxidation of hydrogen from my chemical dictionary:
Magnesium -2.38 Volts
Aluminum -1.66 Volts
Zinc -.763 Volts
Iron (2+) -.409 Volts
Nickel -.250 Volts
Lead -.126 Volts
Copper +.34 Volts
Iron (+3) .771 Volts
Silver +.799 Volts
Platinum +1.2 Volts
Gold +1.489 Volts
I'm not certain, but I would guess that the Iron would break down at the lower voltage listed for the plus 2 (Ferrous) oxidation state first, so that is what I would use to gauge, as I know that if you join iron plumbing to copper without a dielectric, in general your iron pipe will corrode away. I seem to recall a historical article where the Brits built a copper sheathed boat in the age of wooden warships, but ran into a problem where all of the iron nails used to hold it together corroded away within weeks in sea water.