Greg Koenig, writing for iMore, digs into the durability of the various Apple Watch finishes.

One bit in particular I found fascinating was this discussion of the space black finish, something very difficult to pull off well in traditional watch case finishes:

Enter two technologies: The Physical Vapor Deposition (PVD) plating process and Diamond Like Carbon (DLC) materials.

In the basic PVD process, a part is cleaned thoroughly and placed in a vacuum chamber, along with a consumable sample of plating material. Once the air is evacuated from the chamber, the material sample is vaporized by a heater and eventually condenses on the target part. PVD is a highly competitive, advancing technology with applications across many fields — anti-reflective, UV blocking, scratch resistant sunglass coatings? PVD — and the process is often heavily modified. The gist remains the same.

The PVD process is used to create a vast array of coatings, but the current gold standard for hardness and wear resistance is DLC. Essentially, a DLC coating is a 1-3 micron layer of carbon that self arranges into a structure similar to that found in a diamond, thus imparting some of a diamond’s surface hardness properties. In fact, many of the attempts to create synthetic diamonds revolve around modifying the basic PVD DLC process in order to “grow” a stone. The term “DLC” itself isn’t just one kind of coating, there are 7-8 different basic chemistries, and each manufacturer of equipment and service provider often creates their own proprietary recipe and processes. (Tungsten DLC, for example, deposits a layer of tungsten on the part before the DLC layer is applied, promoting better adhesion).

So just how tough is DLC? The best way to put it is that the watch industry is a second or third tier user of DLC coatings. The vast majority of research and application of DLCs goes into highly engineered components that depend on DLC’s hardness, friction reduction, corrosion resistance, and tribology advantages. (That’s the study of how one material interacts with another during contact and sliding.) You’ll find DLC coatings on shock absorbers and engine pistons in F1 cars, across the leading edges of fan blades in jet engines, coating critical medical implants, and the cutting tools inside the CNC mills and lathes that made the Apple Watch itself. (DLC extends cutter tool life, improves cut quality and allows for dramatic feed/speed increases.)

I find this fascinating. Apple has gotten really good at creating durable finishes for their products. I’ve noticed that every generation of iPhone I’ve owned has shown less and less wear on the case and screen. I suspect the Apple Watch is a beneficiary of all that durability R&D.