Your rugged sports watch may be able to survive all kinds of environments and decades of wear and tear, but it will often end up with battle scars to show it. You can keep your modern watch away from real life to avoid this, but watch companies are using a range of interesting technologies to help keep metal scratch-free – and that means more worry-free wear for you.
Of course, some people like patina and wabi-sabi, but a watch that will work and looking new for longer is a compelling proposition. The techniques used by watchmakers to increase scratch resistance not only keep a watch new, but they convey a sense of overall ruggedness, technical superiority, and an interesting history in the product. For a watch buyer, these features offer a lot of value – and while they can be a bit daunting to figure out, they’re also pretty darn fascinating.
When talking about the properties of a metal, terms like strength and hardness are deceptively familiar but have specific meanings in engineering and materials science. While strength refers to the tendency of a metal to break or bend under stress (which is not really a problem in watches), hardness is what you’ll want to take note of if you’re concerned about scratch resistance. Vickers is the most commonly used hardness measurement in the watch industry, with 18k yellow gold being around 150 HV (Vickers), 316L stainless steel around 200 HV, and diamond at 10,000 HV. .
Since there are many factors that affect a material’s physical properties (and can get quite technical), it’s easier to look at a few examples of the three most common approaches to increasing scratch resistance in watchmaking: alloys, coatings and surface hardening.
Scratch resistant alloys
Although a metal can be generically called steel or bronze does not mean that its composition is identical to that of other steels or bronzes. The most common steel used in watches is 316L stainless steel (also “marine grade” or “surgical grade”), and it is made from iron with smaller amounts of chromium, nickel, molybdenum and gold. ‘other ingredients which may differ slightly.
Different formulas can affect different properties, and you’ll find that watch companies refer to all kinds of materials which can just be alloys of familiar metals. For example, Rolex’s famous “Oystersteel” is said to be its own 904L stainless steel alloy (which other companies use as well), and it is more corrosion resistant than 316L. To further complicate the problem, it is not only the composition of the metal that can affect its properties, but also the production processes. Metalworkers also need to strike a balance between making a metal harder while not letting it get too brittle.
Gold is notoriously soft, which makes it easy to work with but also quite scratchable. Pure 24k gold is too soft to be used in watches *, so most solid gold watches are quite hard at 18k (75% gold) but remain easily nicked and scratched. The Swiss watchmaker Hublot, experimenting regularly with unconventional materials, has created a mixture of gold and ceramic which he calls “Magic Gold” and which he prides himself on “being scratch-resistant”.
(* In 2014 Bulova used a forging process to harden gold for use in a 24k gold watch.)
The German brand Damasko uses a steel alloy created for aeronautical applications which it calls by the badass sounding name of “ice hardened steel”. Unlike, for example, stainless steel, this alloy does not use nickel and is instead enriched with nitrogen and less than 1% carbon. The brand claims the result is a material that cannot be easily scratched and is superior to surface hardened metals which can still show damage when the underlying (uncured) metal deforms due to impact.
Scratch resistant coatings
This is what it looks like: a coating that serves to protect the material underneath. You will see a bunch of terms and acronyms in the watch industry that refer to different types of coatings that can add color to a case and / or protect it. One of the most commonly used to color cases from gold to black is PVD (physical vapor deposition), which refers to the method of production rather than the coating material itself. The problem with many coatings is that they themselves can get scratched or just wear out over time, becoming especially noticeable when there is a different color underneath.
DLC (diamond-like carbon) refers to a type of coating applied by the PVD process. This is not only responsible for the black color of many of those inevitably badass tactical watches, but it also offers excellent (but not invincible) scratch resistance. Seiko’s DiaShield and Citizen’s Duratect or Super Titanium are examples of clear coatings that add significant scratch resistance without changing the appearance of the finish of the case material.
High-end watches from Breitling to Tudor use DLC as their preferred method of coloring a watch case black. In an example of how Apple has learned the right lessons from the traditional watch industry, however, the premium version of the Apple Watch is made of titanium with a black DLC coating. This basically negates the downside of titanium and leaves you with all the benefits, along with a jet black finish.
Titanium is popular in the aerospace industry for its extreme strength and lightweight properties, but it can end up scratching quite quickly if not properly processed. Titanium is technically harder than typical stainless steel, but the scuffs that you tend to see on titanium are actually the scratches on the oxide layer that titanium naturally forms on contact with air. They can be “polished”, but it is far better to treat the metal specifically to avoid this and deeper scratches. Citizen’s “Super Titanium” is said to be more resistant to scratches than ceramic.
Surface hardening for scratch resistance
An interesting way to increase scratch resistance is to treat standard alloys in a special process. Rather than using a harder alloy or coating on top of the metal, this is a chemical technique in which a surface layer (usually only a few micrometers thick) of the material itself is weathered and significantly hardened. A criticism of this method is that a very hard impact can further dent the softer metal below the surface, causing an “eggshell effect” rather than a scratch. (Were talking very hard impacts, however.)
German watchmaker Sinn is best known (at least among watch enthusiasts) for this technique, which he also combines with other measures of durability and scratch resistance. Sinn calls the process “tegimenting, “ but other companies do similar things under different names such as “kolsterising”. The brand processes various alloys of steel and titanium, but it is said to achieve the greatest hardness when combined with underwater steel, as seen here in the U50 dive watch.
All watch cases from British watchmaker Bremont receive a surface hardening treatment that the brand calls B-EBE2000. This process, according to the brand, involves the metal being “heat treated and defused with carbon, then bombarded with electrons” (seemingly technical, right?) And results in a surface hardness seven times harder than stainless steel. Typical 316L.
This content is created and maintained by a third party, and uploaded to this page to help users provide their email addresses. You may be able to find more information about this and other similar content on piano.io