904L vs. 316L Stainless Steel: What's the Difference?

When selecting stainless steel for highly corrosive environments, both 316L and 904L are popular choices. But what sets them apart-and which one is right for your application? This article compares 904L and 316L stainless steels in terms of chemical composition, corrosion resistance, mechanical strength, cost, and common use cases.

904L vs. 316L Stainless Steel: Chemical Composition

Element	316L (UNS S31603)	904L (UNS N08904)
Chromium (Cr)	16.0–18.0%	19.0–23.0%
Nickel (Ni)	10.0–14.0%	23.0–28.0%
Molybdenum (Mo)	2.0–3.0%	4.0–5.0%
Carbon (C)	≤ 0.03%	≤ 0.02%
Copper (Cu)	-	1.0–2.0%

Summary: 904L contains significantly higher levels of nickel and molybdenum than 316L, along with added copper, which greatly enhances its corrosion resistance in aggressive environments.

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904L vs. 316L Stainless Steel: Corrosion Resistance

316L is highly resistant to general corrosion and pitting in chloride-rich environments. It performs well in marine settings and mild chemical processes.

904L, on the other hand, offers superior resistance to:

Sulfuric acid

Phosphoric acid

Chloride-induced pitting and crevice corrosion

Stress corrosion cracking (SCC)

Thanks to its high nickel and copper content, 904L is ideal for harsh chemical processing and acid handling.

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904L vs. 316L Stainless Steel: Mechanical Properties

Property	316L	904L
Tensile Strength	~485 MPa	~490–710 MPa
Yield Strength	~170 MPa	~220 MPa
Elongation	≥ 40%	≥ 35%
Hardness (Brinell)	≤ 217 HB	≤ 220 HB

Note: Both materials are austenitic and non-magnetic in the annealed condition, offering good weldability and formability.

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904L vs. 316L Stainless Steel:Heat Treatment

Both 316L and 904L stainless steels are austenitic, meaning they cannot be hardened by heat treatment. Instead, their mechanical properties are primarily adjusted through cold working.

Property	316L	904L
Heat Treatable?	Not hardenable by heat treatment	Not hardenable by heat treatment
Annealing Temperature	~1,040–1,120 °C (1,900–2,050 °F)	~1,090–1,170 °C (2,000–2,140 °F)
Cooling Method After Annealing	Rapid air or water quench	Rapid air or water quench
Intergranular Corrosion Resistance	Excellent due to low carbon	Excellent with proper annealing

904L vs. 316L Stainless Steel::Cost Comparison

Due to its high alloy content, 904L is significantly more expensive than 316L-often by 2–3 times depending on market conditions. It's generally chosen only when 316L or even 317L is insufficient for the environmental demands.

904L vs. 316L Stainless Steel:Weldability and Fabrication

Both grades are weldable using standard techniques (TIG, MIG), but 904L requires greater care due to its higher nickel content, which may lead to hot cracking if improperly managed.

904L vs. 316L Stainless Steel: Applications

316L is commonly used in:

Marine hardware

Heat exchangers

Food and pharmaceutical equipment

Architectural structures

904L is preferred in:

Chemical processing plants

Flue gas scrubbers

Acid storage tanks

Oil and gas offshore platforms

Pulp and paper industry (chloride-rich environments)

 

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