I recently changed the bolt that holds my crank arm on my FSA crank. The nice folks at FSA sent me the new steel bolt to replace the aluminum one and they included a small tube of loctite 641. The instructions for the 641 say to clean all parts with a non residue leaving cleaner, apply the 641 to both surfaces and torque to spec. It also says to allow 24 hours to cure and if you need to disassemble, to follow normal disassembly instructions. I don't know if the 641 is hard to find or not.