If using the brass split jaw joiners, simply line the inside of the rail joiner with aluminum foil.
I know that Brass and aluminum don’t mix.
Why would brass and aluminum foil not mix as well?
I’d use aluminum track joiners or clamps.
John Bouck said:John,
I know that Brass and aluminum don't mix. Why would brass and aluminum foil not mix as well? I'd use aluminum track joiners or clamps.
Since it is a galvanic reaction the result will be the same i.e. the aluminum breaks down. Then you replace the alu foil. 
BTW I remember from more than 50 years back the little debacle on some Zürich street cars where Alu and Steel were used. Together with the inevitable saline moisture due to the road salt it was a fine and expensive mess.
Aha!
The foil is sacrificial.
Just like the zinc plates we put in our saltwater condensers.
Although I’d be too lazy to change out the foil all the time.
Hmm. Totally theoretical here, but what about a double layer? Outside is plastic (saran wrap) and inside is copper foil? But what do I know? I am looking at plastic rail!
My experience is with Llagas Creek code 250 aluminum track and Hillman clamps. I put foil inside the brass clamp, held in place with “No ox” or equivalent. My theory is that electrons are LAZY, and rather than fight their way into the brass, they just stay in the aluminum rail, foil, then rail!
I’ve also had good luck applying a couple of drops of Automatic Transmission Fluid Dexron III to the rail. Seems to keep the rail cleaner and improve electrical contact between the rail and the pick ups.