One of the most commonly used processes for the production of a metal coating on a solid substrate is the electroplating, or also known as electrodeposition. During the electroplating process, a direct electric current is used to allow the reduction of cations of the metal. However, a plastic solid substrate is usually non-conductive, and therefore direct electroplating is not feasible.
For this purpose, a series of steps is required to pre-treat the surface and allow the metal coating deposition.
Starting with a pre-treatment of the surface, etching in chromic acid bath solutions is currently used to enhance the metal adhesion. The chromic acid bath induces great occupational safety and environmental risks, as it utilized hexavalent chromium, know for its carcinogenic and toxic effects.
Moving to the second pre-treatment step, surface activation is achieved employing Sn-Pd baths to disperse nucleation sites and ensure the electroless metal deposition can take place. The palladium used in the baths is a critical raw material, which increases the cost of the process significantly.
The third step is the metallization of the surface, using the electroless plating process. During this process, a thin metal film is deposited on the surface. The plastic surface is now conductive due to this thin film that allows to proceed with the main metallization process of electroplating.
During the electroplating process, a metallic coating of proper thickness is deposited on the plastic surface, enhancing the wear and corrosion resistance, as well as the aesthetic appearance of the plastic component.
The FreeMe project aims to eliminate the use of hexavalent chromium (Cr6+) and palladium (Pd) from the Plating on Plastics (PoP) process, based on REACH compliant chemicals, avoiding toxic compounds and ensuring long-term sustainability.