Usually buy Noalox from Amazon but I believe Home Depot carries it.
http://www.homedepot.com/h_d1/N-5yc...=-1&keyword=noalox&storeId=10051#.UD6gYtZlRuA
Guessing the tank is completely sealed from the battery tube? I was worried about Noaloxing the top threads.
Now to find something to lube up the top threading.