Stainless steels are well-known for their corrosion resistance, but certain grades outperform others. For many years, Rolex employed the popular stainless steel grade 316L, which is the norm for approximately 95% of the watch industry. In 2001, however, they switched from 316L to 904L and are now the only watchmaker in the world to employ this grade for their watchcases. The main reason for the shift was because 904L has a greater pitting resistance equivalent number (PREN) measurement than 316L, which has roughly 26 PREN.
There are other benefits to the grade, particularly in watchmaking. 904L polishes exceptionally well, producing a highly polished brushed finish. Rolex also mentions the greater chromium concentration of 904L, which they claim creates an impermeable barrier on the steel’s surface when exposed to oxygen. This implies that if the watch is scratched, the chrome oxide barrier fills and covers it immediately, limiting the possibility of corrosion. Rolex is particularly pleased of the fact that it uses 904L, describing it as another step ahead in their pursuit of excellence. They’ve even created an advertisement extolling the benefits of this stainless steel grade.
Unfortunately, Rolex does not acquire their stainless steel from us, but 904L is becoming increasingly popular, particularly in the petrochemical industry.
