Using bronze, brass, or gold in your design? Think PVD.
Physical Vapour Deposition (PVD) is a collective set of processes used to deposit thin layers of material to metal surfaces to give them a hard durable coating. It is commonly used in the architectural and interior design industry to add colour to stainless steel and help extend the life of a number of different architectural products internally and externally. The PVD processes are carried out in a high vacuum with temperatures ranging between 150°C and 500°C and are environmentally friendly.
The PVD process consists of three fundamental steps:
1. Vaporisation: this is the process where a high energy source bombards a target and dislodges atoms from its surface, vaporising them.
2. Transportation: this involves the movement of the vaporised atoms from the target to the subject piece being coated.
3. Condensation: this is the final stage of the process where the vaporised atoms bond to the subject’s surface, and they can even penetrate the surface slightly, to give a lasting level of adhesion.
There are different types of PVD processes that can be applied to certain types of materials:
- Arc Evaporation – this process involves an arc with a diameter just a few microns thick being run over the solid, metallic coating material, causing it to vaporise. Due to the high currents and power densities used, the vaporised material is almost totally ionised and forms a high-energy plasma. The vaporised ions combine with the reactive gas that is introduced into the chamber and they strike the subject with high energy. Therefore they are deposited as a thin and highly adherent coating.
- Sputtering – in this process the parts that are to be coated are heated first. They are then ion etched by bombardment with argon ions. This makes the metal surface pure and clean and free from any contamination. A high negative voltage is then applied to the sputtering sources which contain the coating material. The resulting electrical gas discharge leads to the formation of positive argon ions that are accelerated in the direction of the coating material. Once the vaporised atoms react with the gas that is introduced into the chamber they deposit on the subject part, and the result is a thin coating.
- Enhanced sputtering – the principle of enhanced sputtering is similar to the sputtering process. However a low-voltage arc discharges in the centre of the chamber making the plasma intensity several times greater and there procures a much higher degree of ionisation.
- Ion Plating – this process uses reactive electron beam evaporation. While sputtering uses bombardment t with argon ions to remove coating material from the subject, in ion plating, the metallic component of the coating material is evaporated by a low-voltage arc.
The PVD process is becoming more common in the architectural and interior design industry due to architects and designers wanting new and innovative finishes to products. PVD coated products such as metal meshes and perforated sheets are fine to be used externally and will not wear, scratch or corrode. By using PVD you are able to mimic more expensive materials such as bronze, brass and gold.