FFg, Howdy is correct about using graphite (molykote), but with dissimilar metal, the expansion coefficient due to heat is not the same. I use an anti-seize thread lubricant which is a powdered copper base substance. The name is VersaChem and guards against seizing to 2,000f.
I use a small amount applied with a pipe cleaner, it does not require much. I buy this compound from Auto Zone or NAPA and the like. It has never failed me.
The key to nipple maintance is the correct fitting nipple wrench. Buy a good one and not the CVA.