Dont use alminium nipples. Titanium even with ti prep will gall against any material it is in cintact with especially under any type of tension so adjustment will become very difficult. If you really need to use aluminium rather than brass self lubricating and meaninglessly heavier nipples use some mastinox assembly compound (also known as Yackshit because of the yellow colour) Just be very carefull in case the health and safety police find out as its highly poisonous.