Black coating (PVD / DLC)

PVD and DLC are two distinct processes, often confused, that both produce a black finish on metal watch surfaces. Keeping them separate is the first duty of anyone describing them.

PVD stands for Physical Vapor Deposition. In a vacuum chamber, the coating material — typically titanium nitride or zirconium nitride — is vaporized and deposited onto the base metal surface layer by layer. The result is a thin, hard film that adheres to stainless steel without appreciably altering its dimensions. The 1972 Porsche Design Chronograph 1 was the first commercial watch with an entirely black PVD-coated case: a technical choice before an aesthetic one, designed to reduce reflections under operational conditions. The process has remained essentially the same since then, though the deposited materials have diversified.

DLC — Diamond-Like Carbon — is an amorphous carbon coating, chemically closer to diamond than to graphite. Surface hardness is significantly superior to standard PVD: it's measured on the Vickers scale and in certain DLC coatings exceeds 3000 HV, compared to 2000-2500 HV for a good PVD. The appearance is opaque or satin black, often described as stealth. DLC is also applied under vacuum, but using plasma processes different from classical PVD. On the wrist, the difference shows over time: a well-applied DLC resists daily impacts better than PVD, which tends to chip on the edges of lugs and case screws sooner.

Both treatments protect the underlying metal from surface abrasion and atmospheric corrosion, but neither is permanent. On cases worked with alternating brushing and polishing, the coating tends to wear first on the polished surfaces, where contact friction is greatest. I've seen calibers treated in black PVD on plates and bridges — the caliber 2967 is a documented example — where the contrast between hand-polished edges and the black surface produces a visual reading of the finishing that would be lost on a raw bridge.

A note that technical datasheets almost always omit: the final color depends on the deposited material, not just the process. Titanium nitride gives a warm black; chromium nitride tends toward anthracite gray; the pure carbon of DLC is the coldest and deepest black of the three. Anyone choosing a black watch should know which process they're investing in.