Nickel Anti-Seize???
Ford has a problem on their aluminum 5.4 modular engine with the spark plug breaking upon removal, leaving behind part of it in the hole. (They even came up with a special tool to remove it!) To prevent this from happening they recommend coating part of the spark plug with nickel anti-seize as shown in the illustration here: https://www.enginebuildermag.com/201...lar-engines/2/