Stainless steel 316L vs 904L is widely used in the industrial sector due to its cost-effectiveness and general properties such as corrosion resistance. Specifically, 904L is best suited for use in harsh environments due to its acid resistance. Whereas 316L is used in chlorine environments. In this article, you will be helped to choose the right material between 316L and 904L by understanding the differences between 316L and 904L composition, properties, and applications.
316L is a versatile industry workhorse, while 904L is a high-performance specialist. So how do you know when to stick with your trusted 316L and when you must upgrade to the higher-quality 904L?
This guide will provide a comprehensive comparison to help you make an informed decision.
316L Stainless Steel Definition and Types
UNS S31603 stainless steel is also known as austenitic stainless steel with a low carbon content. AISI 316 L consists of chromium (16-18%), molybdenum (2-3%), and nickel (10-12%). 316L is resistant to corrosion from chlorine environments and reducing acids of the sulfuric acid type due to the presence of molybdenum. Due to the low carbon content, UNS S31603 is softer and more ductile, making 316L easier to machine than other stainless steel grades.
904L Stainless Steel Definition and Types
Austenitic stainless steel containing high alloying elements is called 904L. It has high corrosion resistance to harsh and severe corrosive environments. Other names for 904L include:
- UNS N08904
- ISO 904L
- EN 1.4539
- AISI 904L
- SUS 904L
- SS2562
Stainless Steel 316L vs 904L – What’s the Difference
Applications of Stainless Steel 316L vs 904L
316L Stainless Steel:
316L, also known as austenitic stainless steel, has high corrosion resistance in chlorine environments. 316 is biocompatible and can be cleaned and sterilized. 316L also has efficient heat transfer properties and is durable, which is why it is used in a wide range of applications listed below.
- Marine Hardware
- Chemical processing equipment parts
- Medical implants
- Pharmaceutical equipment
- Heat exchangers
- Valve and pump parts
- Springs
904L Stainless Steel:
904 L is also used in cooling systems and heat exchangers in Marin due to its good corrosion resistance in harsh environments, especially acidic environments. All these characteristics make 904 L suitable for the applications listed below.
- Oil and gas industry equipment
- Pulp and paper processing equipment
- Seawater cooling units
- Wiring in electrostatic precipitators
- Chemical containers
- Gas scrubbing systems
- Heat exchangers
Advantages and Disadvantages of 316L and 904L Stainless Steel
The advantages and disadvantages of UNS S31603 and UNS N08904 are explained below:
Advantages of AISI 316 L:
- 316L is very versatile.
- Excellent corrosion resistance to chloride-rich environments such as the ocean.
- 316L is cheaper than 904L due to less alloy content.
- Better weldability compared to 904L.
- High tensile and yield strength. Less likely to suffer from stress corrosion cracking.
Disadvantages of AISI 316 L:
- Poor corrosion resistance compared to 904L in acidic media.
- Lower toughness compared to 904L.
- Cannot withstand high temperatures.
Advantages of AISI 904 L:
- Excellent corrosion resistance to reducing acids such as sulfuric acid and phosphoric acid.
- Suitable for sensitive applications due to its non-magnetic nature.
- Resistant to high temperatures.
Disadvantages of AISI 904 L:
- High cost
- Poor weldability and machinability.
Chemical Composition of Stainless Steel 316L vs 904L
The performance of any alloy begins with its chemistry. The significant price and performance difference between 904L and 316L comes down to the higher concentration of valuable alloying elements in 904L.
The chemical composition of AISI 316 L and AISI 904L is as follows:
Element | AISI 316L Stainless Steel (%) | AISI 904L Stainless Steel (%) |
Fe | Balance | Balance |
Cr | 16.0 – 18.0 | 19.0 – 23.0 |
Ni | 10.0 – 14.0 | 23.0 – 28.0 |
Mo | 2.0 – 3.0 | 4.0 – 5.0 |
Cu | – | 1.0 – 2.0 |
C | ≤0.03 | ≤0.02 |
Mn | ≤2.00 | ≤2.00 |
Si | ≤1.00 | ≤1.00 |
P | ≤0.045 | ≤0.045 |
S | ≤0.03 | ≤0.035 |
N | ≤0.10 | ≤0.10 |
Physical Properties of Stainless Steel 316L and 904L
The table below gives a numerical comparison of 316L and 904L stainless steel.
| 316L Stainless Steel | 904L Stainless Steel |
Density | 7.99 g/cm3 | 8.00 g/cm3 |
Melting point | 1371-1400°C（2500-2552°F） | 1350-1400°C（2462-2552°F） |
Magnetic | Non-magnetic in the annealed state | Non-magnetic |
Thermal Conductivity | 16.0 W/m·K（100℃） | 12.6 W/m·K（100℃） |
Thermal Expansion Coefficient | 16.0 μm/m·K (0-100 degrees Celsius) | 15.0 μm/m·K (0-100 degrees Celsius) |
Resistivity | 0.074×10^-6Ω·m | 0.085×10^-6Ω·m |
Specific Heat | 500 J/kg·K | 450 J/kg·K |
Corrosion Resistance of Stainless Steel 316L and 904L
While both ISO 316L and ISO 904L perform well in corrosive environments, 904L is highly resistant to corrosion in high chloride environments. 316L is highly recommended for corrosion-resistant applications, but only for general use. 904L is used in specific severe conditions such as heat exchangers. 904L is more susceptible to stress corrosion cracking when tensile loads are applied in severe environments than 316L.
This is where 904L truly justifies its “super austenitic” title and its higher cost.
General Corrosion & Acids
While 316L handles mild corrosives well, it can struggle with strong acids like sulfuric and phosphoric acid. The combination of high Molybdenum and added Copper in 904L gives it outstanding resistance to these chemicals, even at higher concentrations and temperatures. This makes it a go-to material for chemical processing plants.
Pitting and Crevice Corrosion
In environments rich with chlorides (e.g., seawater, coastal areas, desalination plants), stainless steel is vulnerable to localized pitting and crevice corrosion. The resistance to this is often measured by a PREN (Pitting Resistance Equivalent Number).
316L PREN: ~24-26
904L PREN: ~34-37
The significantly higher PREN score of 904L indicates a far superior ability to resist pitting corrosion, ensuring longer equipment life in chloride-rich media.
Stress Corrosion Cracking (SCC)
SCC is a form of catastrophic failure that can occur when a material is under tensile stress in a corrosive environment. Standard austenitic grades like 316L are susceptible to chloride-induced SCC.
Thanks to its extremely high nickel content, 904L offers excellent resistance to SCC. This is a critical safety and reliability factor in applications like heat exchangers and pressure vessels.
Mechanical Properties of Stainless Steel 316L and 904L
The mechanical properties of a stainless steel grade determine its suitability for application under specific conditions. The mechanical properties of stainless steel grades ISO 316L and ISO 904L are described below:
Hardness of Stainless Steel 316L and 904L
The Brinell, Vickers, and Rockwell hardnesses of stainless steel grades ISO 316L and ISO 904L are shown in the table below.
| 316L Stainless Steel | 904L Stainless Steel |
| Brinell hardness | 146 – 217 | 170 – 220 |
| Vickers hardness | 152 – 209 | 180 – 230 |
| Rockwell hardness | B79-B95 | B85-B96 |
Strength of Stainless Steel 316L and 904L
The strength of 316L and 904L is shown in the following table:
| 316L Stainless Steel | 904L Stainless Steel |
Tensile Strength | 485-620MPa | 490-690MPa |
Yield Strength | 170-310MPa | 220-450MPa |
Elastic Modulus | 193 gallons | 200 gallons |
Weldability and Machinability
Among the stainless steel grades ISO 316L and ISO 904L, 904L is ductile and easy to weld and machine compared to 316L. 316L contains alloying elements compared to 904L, which makes it difficult to weld and machine.
Surface Treatment and Finishing
316L and 904L stainless steel surfaces are subjected to surface treatments such as polishing, electropolishing, and passivation. 316L has a better surface finish compared to 904L.
Heat Treatment
Both stainless steel grades ISO 316L and ISO 904L can be annealed to eliminate internal stresses and improve ductility. 316L can be annealed at 1010 – 1120°C, while 904L can be annealed at 1095 – 1175°C.
Cost vs. Lifetime Value
904L is significantly more expensive than 316L stainless steel. This is directly due to its high nickel and molybdenum content, two expensive metals.
However, decisions should not be based solely on initial cost. The total lifecycle cost should be considered:
If 316L is sufficient, then using 904L is an unnecessary expense.
But if 316L fails prematurely in a harsh environment, the cost of downtime, replacement, and potential damage will far outweigh the initial savings.
Investing in 904L in the right application from the start is a strategic decision that will pay off handsomely in reliability and longevity.
Practical Guide: When to Choose Which Steel
Choose 316L Stainless Steel for:
Food and beverage processing
Pharmaceutical production (where not exposed to highly corrosive agents)
Architectural and marine hardware in moderate chloride environments
General chemical equipment handling less aggressive chemicals
Most water treatment applications
Basically, 316L is the perfect choice when you need a step up from 304L but don’t face the extreme conditions that demand a super austenitic grade.
➡️ Explore our 316L Stainless Steel Products
Choose 904L Stainless Steel for:
Equipment for handling sulfuric, phosphoric, and acetic acids
Offshore oil and gas platforms, especially for sour gas processing
Seawater cooling systems and desalination plants
Flue-gas desulfurization (FGD) systems in power plants
Pulp and paper bleaching equipment
High-end, luxury watches known for their sheen and corrosion resistance (like Rolex)
In short, if your application involves high temperatures, high chlorides, or strong acids, and the risk of failure is unacceptable, 904L is the right choice.
Selecting the right stainless steel material is a critical engineering decision. If you are weighing the pros and cons of a specific project, our team of stainless steel experts is here to help. We can analyze your operating conditions and provide data-based recommendations to ensure you achieve the best balance between performance and cost.
Contact Huaxiao Metal today for a free consultation or a quote on our premium 316L and 904L materials.
In Conclusion
The following table explains the differences between UNS S31603 and UNS N08904.
| 316L Stainless Steel | 904L Stainless Steel |
Composition | Fe, chromium (16-18%), nickel (10-14%), molybdenum (2-3%) | Fe, chromium (19-23%), nickel (23-28%), molybdenum (4-5%), copper (1-2%) |
Corrosion Resistant | Good corrosion resistance, especially suitable for chlorides and reducing acids | Excellent corrosion resistance, especially suitable for resisting local corrosion from reducing acids such as chlorides and sulfuric acid |
Price | Not that expensive | More expensive due to higher alloy content |
Weldability | Easier to weld | Poor weldability due to higher alloy content |
Application | Food processing equipment, chemical tanks, marine environments | Piping systems, pollution control equipment, heat exchangers, oil and gas industry, chemical processing |
Hardness | Rockwell hardness less than 95 | Rockwell hardness less than 95 |
Density | 7.99 g/cm3 | 8.00 g/cm3 |
Melting Point | 1371-1400°C（2500-2552°F） | 1350-1400°C（2462-2552°F） |
Magnetic | Non-magnetic in annealed state | Non-magnetic |