In the world of stainless steel, two popular stainless steels stand out: 316L vs 904L. Both stainless steel have their own unique properties and applications. Both 316L and 904L are commonly used in watches, medical applications, and marine applications. The most common stainless steel used in the watch industry today is 316L. 904L steel is an austenitic stainless steel like 316L steel, but the chemical composition of 904L stainless steel contains more chromium (19%-23%) and molybdenum (4%-5%), making 904L more resistant to corrosion than 316L.

In this blog post we delve into the definition of 904L steel vs 316L and their benefits, and compare them head to head to determine the applications of 904L steel and 316L in the watch industry, and which stainless steel you can choose when designing a watch to suit your needs.

What is 316 stainless steel

Stainless steel is a large category of steel alloys, including 904L, 316L, 316L and 304 stainless steel. so what is the relationship between these?

304 stainless steel is a T300 series austenitic stainless steel, its chemical composition includes about 18% chromium, 8% nickel, up to 0.08% carbon, is more suitable for kitchen utensils, hardware production. While 316 stainless steel is composed of chromium (16%), nickel (8%), molybdenum (2%) and traces of carbon, which means that the 316 material has excellent ductility and is resistant to high temperatures, corrosion, and so on.

316L is a low carbon variant of 316 stainless steel. 316L has less than 0.03% carbon in its chemical cost, meaning that 316L has better resistance to intergranular corrosion.

For example, the “L” in 316l stainless steel stands for “low”, indicating that the alloy has a very low carbon content, which effectively prevents carbide precipitation. 316L steel is commonly used in the chemical and petrochemical industries, food processing, pharmaceutical equipment, medical devices, jewelry, and luxury watches (especially dive watches) applications.

What is 904l steel

Like 316L, 904L steel is a low carbon austenitic stainless steel. Its chemical composition includes nickel (up to 28%), chromium (up to 23%), molybdenum (up to 5%), manganese (up to 2%), silicon (up to 1%), and trace amounts of iron and carbon.

Similarly, “L” indicates that 904L is a low-carbon variant of standard 904 stainless steel, containing no more than 0.02 percent carbon.Due to the higher nickel and chromium content of 904L, as well as the addition of copper, as 904L is more corrosion resistant than 316L.

Some people are familiar with 904L steel because it is a metal commonly used in the production of Rolex watches, which speaks to its high quality and durability.

The chart below summarizes the main compositional differences between 316L VS 904L:

904L vs 316L

Corrosion resistance

The corrosion resistance of 904L is better than 316, because the chemical composition of 904L contains more elements that help stainless steel to perform in various corrosive environments, such as the nickel content of 904L is higher than that of 316L. In addition, you can also check the PREN value of the two to determine their corrosion resistance, through the calculation of the 904L, the average PREN value of 36.7, while 316L’s The PREN value is only 26, which means that 904L is more resistant to corrosion, such as seawater.
This is why Rolex switched to 904 steel. Rolex was concerned that the 316L watch case would corrode and ruin the water resistance of the watch.

Durability

Oxygen in the air reacts with the chromium in 316L and 904L stainless steel to form a protective layer of chromium oxide on the surface of the stainless steel. Since 904L contains more chromium than 316L, 904L provides longer and stronger protection.

Cost

The price of one ton of 904L steel is 2 to 3 times of 316L. But for the watch industry, the weight of a case is usually a few dozens of grams, so the price difference of the case embryo is not significant.
Due to the processing difficulty of 904L, 904L processing requires special equipment. In addition, because the main material of watch case is 316L instead of 904L, things are more expensive than rare. The cost of 904L stainless steel case is about 2 times of 316 case.

Hardness

Both 904L and 316L stainless steel have Rockwell hardness values below 95, which is the hardness value of most stainless steels.

So 904L steel is not harder than 316L. However, since dive watches are subject to corrosion from seawater, and 904L steel provides stronger protection, 904L is still superior.

Which is better 316L VS 904L

To determine whether to use 904L or 316L for a watch case or strap, you need to consider what your watch’s positioning or selling point is. If you want to create a brand of diving watch, then choose 904L steel watch, because 904L is more resistant to corrosion. If you just want to buy an economical and practical watch, choose 316L stainless steel. when manufacturing watch parts, most factories nowadays choose 316L or 304 stainless steel. Most factories choose 316L steel when manufacturing watch parts, but our watch company can provide 304, 316L and 904L according to customers’ requirements.

Conclusion-904L vs 316L

In summary, the choice between 316L vs. 904L stainless steel in the watch industry depends on the specific requirements of the application. While both alloys offer excellent corrosion resistance, 904L steel excels in highly corrosive environments, while 316L stainless steel offers a more cost-effective solution. Understanding these properties and differences will help you make the right choice.