PVD coating – a finish for all seasons
By Ian Desmond
PVD coated coloured stainless steel is used in the creation of sculpture, architecture, jewellery, phones and is used for interiors and exteriors. We look at this very versatile medium.
PVD coating – a spectrum of colour options
When it comes to stainless steel you’re not just restricted to simply silver. There are a rainbow of colour opportunities which can be achieved through the Physical Vapour Deposition (PVD) process.
The process of PVD coating
During the process, first of all the stainless steel is cleaned to make sure that the coating will bond well. The steel is then placed in a vacuum chamber with a “target” metal; this will be used to create the coating. A high vacuum level is needed in the coating chamber, then a small amount of argon gas is introduced. A high voltage circuit is used in order for the stainless steel and target to bond or adhere. This allows the argon ions to bombard the target to release atoms of the target metal, which are deposited on the stainless steel substrate as the coating. This PVD process is called sputtering; resulting in the deposition of plasma on the stainless steel surface which gives it its new strength and shine.
The coloured surface coatings that can be obtained using PVD include: gold (TiN), rose gold (ZrN), bronze (TiAlN), blue (TiAlN), black (TiAlCN), as well as a dark red (ZrN). This ceramic coating which is produced is very thin, making the texture of the underlying finish still visible. These PVD colours will not fade over time and have the benefit of being more uniform in appearance and more abrasion-resistant than colouring which is done by the electrochemical processes.
Wear and weather resistant
The stainless steel’s original texture and structure is not changed however the PVD process not only increases the product’s longevity but also reduces its maintenance. Although it has been used for applications that need to be wear and weather resistant, like door hardware, it is important to say that the colour can be damaged if it is attacked very aggressively and in some instances may not be repairable. PVD lasts longer than other coatings which are a similar thickness.
An environmentally friendly process
The PVD process is also more environmentally friendly than alternatives such as electroplating and painting. Unlike these there are no gases, water waste and other residue released. Also important to note is that the colouring process does not limit the recycling value of the stainless steel.
Uses for PVD coated stainless steel
PVD coloured stainless steel is well used in the architectural and industrial design industry. Examples include;- stainless steel curtain walls, cladding and profiles for hotels and casinos, shopping centres, railway stations and for the facades and fit-outs of high-end retail stores.
PVD coated stainless steel can also be used in the transport industry such as;- ceiling and wall cladding to shipping or seating, skirting and panelling on trains.
At the smaller end of the scale the coloured steel can be used for anything from display cases, furniture, lighting fixtures, to door handles and taps./p>
The PVD process can also be used on stainless steel jewellery – achieving some striking colours. The PVD stable colours are gold, rose gold, coffee, black, dark grey, and blue. All these colours are available in a polished, satin or matt finish according to the product surface polish finish.
For gold and rose gold finish, real gold (maybe 14K or 18K) is evaporated and deposited on the part under high temperatures or via ion bombardment. The shade of the gold achieved is according to the gold content of the target. Colour pigments or gas together with the TiN layer are used to achieve other shades.