Many installers wonder which type of stainless steel to choose from the CATS system: 316L or 304? The decision mainly depends on the water hardness and the environmental conditions where the installation will take place.

This guide explains the technical and practical differences between both grades to help you select the most suitable option for your project.

Main differences between stainless steel 316L and 304

Both are austenitic stainless steels widely used in plumbing, heating, and HVAC applications. Although they share many properties, their chemical composition determines key differences in resistance, performance, and cost.

Chemical composition

• Stainless Steel 316L: Contains 2–3% molybdenum, which improves corrosion resistance in environments exposed to chlorides or chemical agents.
• Stainless Steel 304: Has a simpler composition with a lower molybdenum content (less than 0.03%).

Corrosion resistance

• 316L: Offers superior corrosion resistance, especially in environments containing chlorides and other aggressive agents. It is ideal for marine and chemical applications.
• 304: Provides good corrosion resistance in a wide variety of environments but is less resistant than 316L in the presence of chlorides.

Resistance to stress corrosion

• 316L: Has better resistance to stress corrosion cracking (stress corrosion cracking) than 304, making it more suitable for applications where structural integrity is critical.
• 304: Although it offers resistance to stress corrosion, it is not as robust as 316L in this respect.

Soldability

Both grades are easy to solder, but 316L can be more sensitive to pitting corrosion in heat-affected zones after welding. A post-weld heat treatment is recommended to maintain optimal corrosion resistance.

Typical Applications

• 316L: Commonly used in marine, chemical, food processing, and medical environments where high corrosion resistance is required.
• 304: Suitable for a wide range of applications, including kitchen equipment, architectural components, medical devices, and storage tanks.

Cost

316L stainless steel is generally more expensive, but it offers higher durability in harsh environments. 304, on the other hand, remains a cost-effective and high-performing choice for standard conditions.

High-Temperature Resistance

Both materials maintain their strength at high temperatures, but 316L offers slightly better oxidation resistance thanks to its higher molybdenum content.

Conclusion

The choice between stainless steel 316L and 304 depends on the specific requirements of your application. If corrosion resistance in aggressive or marine environments is essential, 316L is the preferred option. However, 304 remains an excellent and economical choice for many general-purpose applications.