According to the coppermind, Aluminium acts as an investiture sink, so any investiture which is put into it will just be "soaked up" by the aluminium, but Aluminium can also be used as a hemalurgic spike, which works on the premise of ripping off a chunk of one's spiritweb, and in a sense 'stapling' into onto the recipient, and to my understanding, your spiritweb and investiture are basically the same thing, so wouldn't the aluminium just absorb it?
Have I missed something, if so someone point it out please, and also please correct any wrong facts i've stated