All water block cooling heads are made of bare rods of electrolytic copper. These rods are milled using a precision-guided CNC machine to make a bare copper water block (cooling head) base.
Nickel electroplating is a technique of electroplating a thin layer of nickel onto a metal object. If a water block is nickel-plated, it means the product is coated with the fine layer of nickel after the milling. The bare copper bases are therefore coated with a fine thin layer of nickel in a submersion bath. The nickel layer is decorative and can provide corrosion and wear resistance.
The so-called 'Nickel water block' is still a pure copper water block, only plated with a layer of nickel. Performance-wise the nickel-plated water block is identical in performance to non-plated (bare) copper water blocks.