The vocabulary of jewelry and goldsmithing can sometimes be quite confusing, especially when you're a novice (or not, as you learn something new every day). But don't panic, we'll explain everything!
What is PVD?
These three letters stand for Physical Vapor Deposition. The acronym stands for a metallization method based on physical vapor deposition by spraying.
There are various specific techniques for applying PVD galvanizing:
- vapor deposition: This method is also known as "vacuum evaporation". It involves the vacuum deposition of a thin, uniform layer of metal onto a product using steam. This process enables precise control of coating thickness.
- Sputtering: Microscopic particles are sprayed onto an object to coat it with a new layer. These particles are attracted to the jewel, forming a very fine, uniform layer. This technique is renowned for its ability to produce highly adherent, uniform coatings on a wide range of materials.
- ionization or ion beam assistance: instead of using simple particles, we use ions (atoms with a little electrical boost) to "bombard" the surface of the jewel. This bombardment does two things: it compacts and smoothes the coating so that it is stronger and adheres better, and it eliminates small imperfections so that the coating is as perfect as possible. Ion beam assistance densifies the coating, improves adhesion and reduces defects by bombarding the substrate with ions during the deposition process.
Many metals can be deposited by PVD (in fact, virtually all the elements of the periodic table in the solid state). Typically, titanium and chromium are used as the base metals, due to their high corrosion-resistance properties. They are then coated with a layer of precious metal, such as gold, or metal alloys. All in vapor form.
Widely used in industry and watchmaking, this process is increasingly being applied to jewelry.
What metals can be coated with PVD?
PVD can be applied to various metals and alloys that can withstand pressure. But it is particularly interesting for stainless steel. Thanks to PVD metallization, we can offer you gold-plated stainless steel. The thickness of this coating on the stainless steel products we sell is not communicated by the manufacturer. It can vary from 0.01 to several microns.
In the case of a steel base, the coating applied is titanium nitride (TiN). The golden hue remains stable: it does not flake and, although it may lighten slightly, it retains its golden appearance without tending towards silver.
On a copper, brass or zamac base, PVD is less attractive, as it would require a primer for the PVD coating to adhere, which would entail an additional cost.
How does PVD work?
Everything takes place in a vacuum chamber, a kind of hermetically sealed metal machine. Inside this chamber is a carousel on which frames are mounted to hang the items to be coated.
Once the articles have been hung, the chamber is closed again, then emptied of virtually all its air, to reach a pressure of one hundred millionth of atmospheric pressure and avoid the presence of impurities. Next comes the deposition phase: process gas is released through the side walls of the chamber. The carousel performs a regular rotary motion, coating and spreading a uniform deposit on the products. When the operation is complete, the frames are removed, followed by the articles.
What are the advantages of PVD?
- A multitude of colors. The sputtering process allows us to obtain different hues, depending on the reactive gases and temperatures used.
- Ion plating is a clean, environmentally-friendly process. It is more environmentally friendly than electroplating. Unlike the electrolytic process, the PVD coating process is non-toxic. It requires no baths, no chemicals, no water consumption, and no gas or other emissions.
- The product becomes more resistant. The product's properties are not damaged. On the contrary! Titanium nitride, a hard, corrosion-resistant metal compound, extends the product's life and resistance. PVD is much more resistant than conventional electroplating, but it is also more expensive.
A quick reminder: what is electroplating? Sometimes incorrectly referred to as galvanizing, electroplating is a method of plating by electrolysis. This method uses an electric current flowing through a liquid bath to coat a metal object with a thin layer of precious metal or metal alloy.
