With 6 sets of power armor, you need a lot of aluminum to keep them in good shape. I was always running out.

So I was happy to finally find a treasure trove of aluminum trays >80 at the fish packing plant in the far northeast. Shortly thereafter, I randomly ran into X6-88, who I thought I left back at the institute. I added him as a companion and offloaded all my junk. Right after that we cleared out the ghouls at Croup Manor and added it to the list of settlements. Then I traded with X6-88 to get my stuff back to put into the recycler.

There were only 60 trays left! He ate 20 aluminum trays in about 5 min.

I knew that companions used the items you give them, but I thought it was only weapons and aids, not junk. He probably also took some steel, circuitry and gas, but I have no way of knowing at this point.

Lesson learned.