Is Alloy 218 better than SS316?
Aug 15, 2025
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For general industrial and marine applications, Alloy 218 often outperforms SS316 in strength and pitting resistance, but it comes with a higher cost. Your choice depends on performance requirements, operating environment, and budget.
Overview of Alloy 218 (Nitronic 50) and SS316
| Property | Alloy 218 (Nitronic 50) | SS316 |
|---|---|---|
| UNS Number | S20910 | S31600 |
| Type | Austenitic stainless steel with Mn, N, Mo | Austenitic stainless steel with Mo |
| Key Features | High strength, excellent pitting resistance, retains strength at cryogenic temps | Excellent corrosion resistance, good formability, widely available |
| Standards | ASTM A182, A240, A276, A312, A479 | ASTM A182, A240, A276, A312, A479 |
Chemical Composition
Alloy 218's higher chromium, nitrogen, and manganese give it superior strength and pitting resistance compared to 316.
| Element | Alloy 218 (Nitronic 50) | SS316 |
|---|---|---|
| C | ≤ 0.06% | ≤ 0.08% |
| Cr | 20.5–23.5% | 16.0–18.0% |
| Ni | 11.5–13.5% | 10.0–14.0% |
| Mo | 1.5–3.0% | 2.0–3.0% |
| Mn | 4.0–6.0% | ≤ 2.0% |
| N | 0.20–0.40% | ≤ 0.10% |
Mechanical Properties
Alloy 218 has ~80% higher yield strength than 316, meaning it can handle higher loads and stress with less deformation.
| Property | Alloy 218 (Annealed) | SS316 (Annealed) |
|---|---|---|
| Tensile Strength | ~ 690 MPa | ~ 515 MPa |
| Yield Strength (0.2% offset) | ~ 380 MPa | ~ 205 MPa |
| Elongation | ~ 35% | ~ 40% |
| Hardness (HB) | ~ 217 | ~ 150–160 |
Is Alloy 218 magnetic?
In annealed condition, it is non-magnetic, similar to SS316.
Corrosion Resistance
In terms of corrosion resistance and pitting resistance, a clear comparison can be made using the Pitting Resistance Equivalent Number (PREN): the PREN of Alloy 218 is approximately 34–36, while that of 316 stainless steel is around 25–27. This result indicates that Alloy 218 has significantly better resistance to chloride pitting than 316 stainless steel, making it more suitable for environments prone to chloride corrosion such as seawater, brine, and chemical processing applications.
Cost Considerations
In terms of cost, Alloy 218, due to its alloying elements and lower supply, is priced at 2-3 times that of SS316; while SS316 is more economical and widely available in the global market.
Can Alloy 218 replace SS316 in all cases?
Not always. It's over-engineered for mild environments where SS316 suffices.
who choose us?
If your project involves seawater, chlorides, or high-strength demands, Alloy 218 is the better choice despite its higher cost. For general use, SS316 offers an economical, reliable solution. GNEE has a large inventory of popular products for you to choose from. They can be processed into a variety of practical product forms, including sheet, coil, tube, bar, and wire. For detailed chemical composition and free samples, please contact our factory today. We offer competitive pricing and excellent service.Email: sales@gneestainless.com
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