DLC coating: Elegant, robust and environmentally friendly

Black watches look chic, but are usually very sensitive and prone to scratches. But since a watch is an everyday object, it should be as robust as possible so that its wearer can enjoy it for a long time. Watches can be made more resistant using various coating processes. An increasingly popular protective coating for watches is the DLC coating. In contrast to galvanic coatings, DLC coatings are environmentally friendly.

What exactly is a DLC coating?

DLC stands for Diamond-like-Carbon. DLC coatings are not only in great demand for watch cases, but wherever parts or components are subjected to heavy loads or rub against each other and therefore have to be particularly robust. This is achieved through the thin-film coating process. The parts coated in this way are particularly resistant and very smooth.

These advantages of DLC coatings are valued above all in machine and engine construction, in the automotive and aviation industries, in micromechanics, and in plastics and metal processing. Coatings of this type are also particularly biocompatible and are therefore also used in medical technology and the food industry. Since no environmentally harmful chemicals are used, DLC coatings are very environmentally friendly.

DLC coating on watches

The jewelry and watch industry also appreciates the finishing with the diamond-like carbon layers.

A DLC coating has many advantages, especially for watches: The wafer-thin but very hard coating not only gives the watch case an elegant anthracite look, it also makes it particularly scratch-resistant. Another advantage of watches with a DLC coating is that they are colorfast and non-allergenic, making them suitable for allergy sufferers.

DLC coating process

Just like metal coatings with titanium nitride (TIN) and zirconium nitride (ZrN), the DLC coating is applied using the PVD (Physical Vapour Deposition) process.

For this purpose, the coating metal is brought into a gaseous form by evaporation or atomization so that it is deposited on the metal object to be coated (e.g. a watch case). In order to avoid a reaction between the gaseous metal and the air, the PVD process takes place in a vacuum chamber.

Properties of DLC coatings

DLC coatings make objects very scratch-resistant, hard, robust and chemically resistant.

Let’s take a closer look at each property:

Hardness

DLC coatings have a high microhardness. This can be up to 3,500 HV. For comparison: Gypsum has a hardness value of 36 HV (notches can be made with a fingernail), fluorite has 190 HV (notches can easily be made with a knife), quartz has 1120 HV (can be used to make notches in window glass) and a diamond has a hardness value of 10,000 HV.

Layer thickness

The layer thickness is only 1 to 3 µm, i.e. 0.001 to 0.003 mm.

Colour

The carbon gives DLC-coated objects an elegant anthracite look, with a dark grey, slightly shiny surface.

Temperature

A major advantage of the DLC coating is that it can also be carried out at comparatively low temperatures of up to 200°C, which means that aluminum, brass and copper can also be coated without any problems. The DLC coating itself is temperature resistant up to 350°C.

Durability

The durability of the DLC coating depends on various factors, such as the hardness of the material to be coated and the number of layers.

Circula ProTrail watch with DLC coating

For our limited-edition, DLC-coated ProTrail, we kolsterized the 316L stainless steel case so that it has a hardness value of 1.300 HV. The harder case reduces the so-called “eggshell effect”. This occurs when there is too much of a difference in hardness between the coating and the substrate, as the harder coating simply flakes off the softer material. Hardening the case makes the DLC coating on the ProTrail even more scratch-resistant and durable.

The case of the Circula ProTrail is also sandblasted, giving the watch a matt finish.

The ProTrail is through the DLC coatings as well

• Particularly smooth (0.02 μm Ra) for a comfortable fit
• Well protected against corrosion, useful for watches subject to heavy wear
• Suitable for allergy sufferers