Although many watch aficionados understand that watches are made from stainless steel, most don’t know much about why they use this metal. Stainless steel is vital for the wristwatch – with the proximity to your skin, you can build up sweat and moisture, making the watch a corrosion magnet. In additon, waterproof watches are especially susceptible – as the threads holding the crown and case back cannot corrode.
Nowadays, most stainless steel wristwatches are made of 316L stainless steel, and for a time, so was Rolex. Even though 316L steel was created in order to prevent rust and pits from salt water and sweat, Rolex was finding excess wear in the case back threads and watch case. Salt and other minerals are the catalysts needed for corrosion and deterioration of the threads holding the case back. They could clearly see that gold and platinum watches didn’t have this corrosion issue, so it needed fixing. In 2003 their entire production line changed to 904L, though it was as early as 1988 that they released their first 904L steel watch with several versions of the Sea-Dweller.
What is 904L Stainless Steel?
Harder and more rust and corrosion-resistant than other steels, this 904L steel can take and hold a polish incredibly well. This is why steel Rolex watches look different than other steel watches. Rolex calls 904L stainless steel a “corrosion-resistant superalloy.” 904L differs from 316L because of extra Chromium, Molybdenum, Nickel, and Copper which gives it improved resistance to acids. 316L is considered a tougher, harder, “marine grade” steel, but it does not have luster and acid resistance of 904L. Rolex utilizes 904L with the greatest of quality control. Once received from Rolex’s steel suppliers, Rolex casts and scans it using an electron microscope that is capable of detecting the slightest structural or surface defect. Rolex has been known to send steel back when it does not meet their exacting specifications. After casting and inspection, the steel is then re-melted in a vacuum to purify it and eliminate any inclusions that would diminish its corrosion resistance and lead to problems in polishing.
Why don’t other manufacturers use 904L steel?
904L steel is more expensive and much more complicated to machine because of it’s hardness. Rolex had to replace most of their steel production line and tools to be able to handle the change. It helps that they make all their parts in-house, most other brands have to get cases made by outside suppliers. These drawbacks prevent other brands (thus far) from taking advantage of this higher quality steel, and remains as an exclusive Rolex perk.
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