3D printed plastic parts can be accurately nickel plated if the plastic is pre-doped with catalyst before printing, according to scientists from Waseda University, Japan.

WasedaU-3d-printed-metal-catalyst

It is an alternative to a conventional technique, where a plain plastic object is dip-coated with catalyst after manufacture, and then immersed in an electroless metal-plating solution. To improve adhesion, a roughening or etching step can be introduced before catalyst coating.

“Their method is actually an improvement over the conventional metallisation process used to coat 3D plastic structures with metal,” according to the university. “While technically sound, the conventional approach produces a metallic coating that is non-uniform and adheres poorly to the plastic structure. The new technique does not require any type of roughening or etching to promote the deposition of the catalyst. These extra steps cause damage to the 3D object and use of toxic chemicals like chromic acid.”

Instead, the researchers used a dual nozzle fused filament printer, printing ABS from one nozzle and ABS doped with the catalyst precursor palladium chloride (PdCl2) from the other. The doped plastic is only used to build surfaces here metal plating is later required.

Despite not needing a roughening step, adhesion of the metal coating was high, according to the university.

Part of the improvement comes from overcoming the hydrophobic nature of ABS, which naturally rejects dip-coated palladium in the conventional process and is the reason for roughening to increase wettability and porosity.

The proof-of-concept technique used a significant amount of palladium – the doped ABS containing 9% PdCl2 by weight. Catalyst concentration was shown to strongly affected the rate of metal deposition.

Waseda University worked with Nanyang Technological University and Yoshino Denka Kogyo.

The technique is covered in ‘Metal-plastic hybrid 3D printing using catalyst-loaded filament and electroless plating‘, published in Additive Manufacturing. This is a clearly written paper that also covers nickel-coating electro-spun ABS fibres. It is available in full without charge.