Beginner's Guide to Watch Case: All You Need To Know About Materials

Stainless Steel Case

Stainless steel - highly resistant to rust, is invulnerable to the corrosion by moisture or sweat. Furthermore, skin irritation arising from donning stainless steel pieces is extremely rare.

This makes the alloy the ultimate and most ideal choice of material for timepieces and jewellery. 

However, there are mainly three types of stainless steel with varying quality due to its purity level: 304, 316L and 904L. Most premium watches use 316L stainless steel to provide high quality products at affordable prices.

To understand the different types of stainless steel, you will first have to learn about what makes up stainless steel. The basic essential blend of metals - carbon, iron and chromium, will be added with varying mixtures of nickel, manganese or nitrogen. 304 and 316L stainless steel are made with nickel in the mixture while 904L is a subgroup of the Silicon-manganese steels. 

304 Stainless Steel

With 18-20% chromium and 8-10.5% nickel, 304 stainless steel is widely used for making common homeware and thus, most watches made from this type of stainless steel are usually lower-end timepieces. Due to its malleability, 304 stainless steel is also more susceptible to corrosion than 316L and 904L stainless steel. This alloy mix also contains more carbon than 316L, giving its significantly darker shade.

304 Stainless Steel Watch Case Image Credit: AliBaBa

316L Stainless Steel

316L stainless steel is more demanded in the watch industry with its higher composition of chromium and nickel, and some molybdenum for better corrosion-resistance. L in 316L stands for low carbon composition. However, it is also widely used in the medical field for surgical instruments. Due to its high resistance to chlorides, stainless steel is also common in petrochemical, food and pharmaceutical industry, nuclear reprocessing and in marine use. 

316L stainless steel is used in products that require a lot of welding because of its stability at high temperatures and high corrosion conditions. Hence, 316L stainless steel is widely used in most high end watches and reliable, resistant dive watches due to its optimal price and qualities like resistance to magnetism.

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904L Stainless Steel

Used for building heat, pollution control and bleaching equipment because of its high resistance to acids, 904L stainless steel is the most expensive metal. However, due to its more expensive production costs and difficulty processing the steel, 904L stainless steel is mostly used by luxury Swiss watch brands. RX even calls it corrosion resistant super-alloy and they have only used this type of stainless steel in their watch production since 18 years ago. Its incredibly fine polishing even gives RX watches its signature look. 904L stainless steel contains more chromium, molybdenum and nickel than 316L, including even copper, manganese and silicon - enhancing corrosion-resistance. 

However, there really isn’t much of a compromise with 316L stainless steel or upgrade with 904L stainless steel. 

PVD

You would have probably seen PVD in some product descriptions before, PVD is actually an acronym for process ‘’Physical Vapor Deposition’’ - the way many materials like stainless steel are strengthened with.

Look out for these indicators on your watch coating:

• IPG comes on watches with a gold colour
• IPS for silver colour
• IPB for black colour

This coating ensures that the watch colour remains unchanged despite years of wear.