The Iron Plating Accessory has to be researched from a Unknown Knowledge sheet. The sheet must have been crafted from 9 Knowledge Fragment. The fragments are put into a Crafting Table with every crafting space containing a fragment. The Plating can be made in the Infusion Altar with 4 iron ingot and an Iron chestplate, also it Consumes 16 Metallum aspect and 16 Defence aspect the Process consumes 50 Vis.
The plating is used to promote the wearer golem's hearts. (Like player iron armor) Appears to not work on all Golems except for the Iron Golem Guardian. To attach it to a Golem you have to Rightclick it with the Plating selected. The Remove of the Golem will not not destroy the Plating or drop it, the Golem will still have the Plating. (How many hearts added is unknown)