We tend to take stainless steel for granted these days, but in the early 20th century, it was still relatively expensive, and the chemical composition hadn’t been perfected yet. Until the 1940’s, sterling silver watches were common, but they often corroded. Various proprietary stainless steel blends competed until standards like 18/8 and 304L arose. Then 316L, which contains at least 2% molybdenum and is very corrosion-resistant, started to become the watch industry standard in the 1960’s-1970’s. Rolex famously uses 904L stainless steel in their watches, but they’re no longer the only ones. And yet even higher-end brands like Patek Philippe show no signs of switching away from 316L. Here’s our breakdown of what you need to know about the 904L vs 316L stainless steel discussion.
![316 (left) vs 904L (right)](https://www.luxurybazaar.com/grey-market/wp-content/uploads/2024/06/316l-vs-904l-header.jpg)
904L vs 316L: Practical Differences
Property | 316L | 904L |
---|---|---|
Corrosion Resistance | Very good | Outstanding, especially to seawater |
Pitting Resistance | 23.1-28.5 PREN | 32.2-39.9 PREN |
Hardness (Rockwell B) | 70-95 HRB (Usually 78-90) | 70-90 HRB (Usually 85-90) |
Scratch Resistance | OK | OK |
Color | Typical medium grey | Brighter/shinier |
Cost | Relatively affordable. widely available | Much more expensive than 316L |
Polishability | Good | Excellent |
Irritates those with nickel allergies | No, not usually | Yes, frequently |
Why Use 904L Stainless Steel?
As you can see from the chart above, 904L polishes easier and appears brighter than 316L. Its biggest objective advantage in the 904L vs 316L debate, though, is its corrosion resistance. Despite 316L already being quite corrosion-resistant, 904L is more appropriate for extended exposure to seawater. That’s the primary reason that Rolex began using 904L in 1985–they’d seen enough of their old dive watches show up for service with pitting.
Rolex’s marketing wizards have been calling their 904L steel “Oystersteel” since 2018. Rolex says their Oystersteel is harder than 316L, while others believe the opposite is true. Rolexes may appear to scratch relatively easy, but that’s probably more about their brushed finish than their chemical composition. In real-life conditions, I can discern no appreciable difference in scratch resistance when it comes to 904L vs 316L.
Most 316L steels will not be hardened to their maximum hardness. The actual end products in the watch world will be about the same hardness.
Reddit user Ofenlicht on 904L vs 316L
![316 (left) vs 904L (right)](https://www.luxurybazaar.com/grey-market/wp-content/uploads/2024/06/316l-vs-904l-2-1024x683.jpg)
It’s worth noting that, technically, “hardness” and “scratch resistance” are different properties, but they are highly correlated.
More on Stainless Steel Watches:
Six New Audemars Piguet Code 11.59 Watches Now In Steel
A Collector’s Guide to the Rolex GMT-Master II Ref. 16710
A Collector’s Guide to the Rolex Submariner Date 16610
Who Uses 904L vs 316L Stainless Steel?
Rolex wasn’t the first to use 904L steel, nor the first to give it a cute name: Some Omega Ploprof models from the early 1970’s were made from 904L steel, which Omega called “Uranus Steel.” Ball released the Railmaster Icebreaker in 2019, which was their first foray into 904L steel watches. Girard Perregaux released a new generation of Laureato chronographs made from 904L that same year.
On the cheaper end, in 2012, the first batch of Bombfrog BT25 Kampfschwimmer watches was made from 904L, vs 316L stainless steel in later generations. With a price point around $300, those first-gen BT25’s are some of the most affordable known 904L watches.
I’m sure a handful of other watches have been released in 904L at this point, but Rolex seems to be the only notable brand fully committed to it. On the whole, 316L stainless steel remains the king of the luxury watch industry. Now let’s take a look at the actual chemical composition of 904L vs 316L.
904L Stainless Steel vs. 316L: Chemical Composition
Property | 316L | 904L |
---|---|---|
Nickel Content | 10-14% | 23-28% |
Chromium Content | 16-18% | 19-23% |
Copper Content | 0% | 1-2% |
Molybdenum Content | 2-3% | 4-5% |
Manganese | 2% or less | 2% or less |
Silicon | 1% or less | 1% or less |
Carbon | 0.03% or less | 0.02% or less |
Iron | (Remainder) | (Remainder) |
![AP Royal Oak chronograph](https://www.luxurybazaar.com/grey-market/wp-content/uploads/2024/06/ap-finish-1024x683.jpg)
What Came Before 316L?
Before 316L, 304L was essentially the standard for stainless steel watches. The “L” signifies low carbon content, which makes the metal more weldable. 304L is still an extremely common type of stainless steel for all sorts of commercial uses, including many affordable watches. 304L is a type of “18/8” stainless steel, meaning it has 18% chromium and 8% nickel. Chromium and nickel provide some anti-corrosive properties.
However, 304L contains no molybdenum, so it’s not nearly as corrosion-resistant as 316L (let alone 904L). Prior to 304L, the world of stainless steel alloys was less standardized, with proprietary brand names like Staybrite and Rolex’s own Rolesium being common in the 1920’s and 1930’s. Note that Rolex now uses the term “Rolesium” to refer to a steel watch with a platinum bezel.
What’s the Best Stainless Steel?
904L vs 316L is only part of the discussion. There are innumerable types of stainless steels produced today. The definition of “best stainless steel” depends entirely on the intended application. Some steels resist corrosion from certain types of chemicals while being more susceptible to others. 904L’s properties make it very well-suited for watches overall, but it’s not the hardest stainless steel on the market.
Sinn makes watches made from German Submarine Steel (a.k.a. “U-Boat Steel”) which is far harder than both 316L and 904L–and more resistant to corrosion from seawater. Their Tegimented Steel, meanwhile, is 316L stainless steel that has undergone an interesting hardening process. Some people rag on it for only being a “surface treatment,” which is technically correct, but it’s not a coating. It differs from PVD in that no separate coating material is applied–the steel’s own surface is hardened through carbon diffusion. It results in a surface that is about 5x more scratch-resistant than untreated 316L. Bremont’s B-EBE2000 hardening process is similar.
![The 904L vs 316L debate is complicated when you consider unique hardening processes](https://www.luxurybazaar.com/grey-market/wp-content/uploads/2024/06/bremont-b-ebe2000-1024x683.jpg)
The stainless steels I’ve discussed so far are all austenitic stainless steel types. Martensitic steel is far harder, but less corrosion-resistant. Notably, Damasko has been making “ice-hardened” martensitic steel since the 1990’s. The process involves nitrogen-enrichment which helps bring the corrosion resistance up to par. Time will tell what other alloys and materials might become industry standards in the future, but for now, the 904L vs 316L steel discussion shows no signs of going away.
More on Watch Materials:
Rolex Rose Gold: Every Everose Watch Produced by Rolex
Top 10 Platinum Watches
What is Rolesor? And Why Doesn’t Rolex Just Say “Two-Tone?”
An Introduction to Common Materials Used in Watchmaking