2205 duplex stainless steel is one of the most widely used corrosion‑resistant materials in the world. Within this grade, the two most common specifications are S31803 vs S32205. Although both belong to the 2205 family, they have important differences in chemical composition, corrosion resistance, and performance that influence material selection for demanding applications.
In this guide, we break down the key differences between S31803 and S32205, compare their properties, typical uses, and help you determine which one is right for your project.
What are S31803 and S32205?
S31803 and S32205 are two official UNS (Unified Numbering System) designations for 2205 duplex stainless steel.
Both are duplex stainless steels, meaning they have a balanced microstructure of ferrite and austenite, combining the strength of ferritic steel and the corrosion resistance of austenitic steel.
Duplex stainless steels offer:
Higher yield strength than standard austenitic grades
Excellent resistance to pitting and stress corrosion cracking
Improved fatigue resistance
Lower cost compared to super duplex grades
Chemical Composition Comparison: S31803 vs S32205
To understand why S32205 is superior, we must look at the ASTM A240 standards. The slight increase in alloying elements makes a massive difference in industrial longevity.
| Element | UNS S31803 (%) | UNS S32205 (%) | Why it Matters? |
| Chromium (Cr) | 21.0 – 23.0 | 22.0 – 23.0 | Increases passive film stability. |
| Molybdenum (Mo) | 2.5 – 3.5 | 3.0 – 3.5 | Enhances resistance to pitting. |
| Nitrogen (N) | 0.08 – 0.20 | 0.14 – 0.20 | Boosts strength and prevents SCC. |
S32205 has higher minimum chromium and nitrogen content and slightly higher molybdenum compared with S31803. This provides better corrosion resistance, especially in chloride‑containing environments.
Performance Comparison: S31803 vs S32205
1. Corrosion Resistance
| Property | S31803 | S32205 |
|---|---|---|
| Pitting Corrosion Resistance | Good | Better |
| Crevice Corrosion Resistance | Good | Better |
| Chloride SCC Resistance | Strong | Stronger |
Due to its tighter chemistry control, S32205 usually performs better than S31803 in aggressive environments such as:
Seawater exposure
Marine piping systems
Desalination equipment
Chemical processing plants
2. Mechanical Strength
| Property | S31803 | S32205 |
|---|---|---|
| Yield Strength | ≥ 450 MPa | ≥ 450 MPa |
| Tensile Strength | ≥ 620 MPa | ≥ 620 MPa |
Both grades exhibit high mechanical strength, approximately twice that of 300‑series stainless steels. They also have excellent fatigue performance.
Pitting Resistance: The PREN Advantage
When comparing different steel grades, PREN (pitting corrosion equivalent value) is an indicator that engineers need to consider.
UNS S31803 PREN: Approximately 32
UNS S32205 PREN: Approximately 34 – 35+
The Result: S32205 provides significantly better protection against crevice corrosion and pitting in high-chloride environments like seawater.
Cost Comparison: S31803 vs S32205
When selecting 2205 duplex stainless steel for your project, cost is an important factor. Although both S31803 and S32205 belong to the 2205 family, their pricing differs slightly due to chemical composition control and performance:
| Grade | Typical Price Range | Notes |
|---|---|---|
| S31803 | Lower | Standard 2205 duplex steel, suitable for general industrial use with good corrosion resistance. |
| S32205 | Slightly Higher | Tighter chemical composition control (higher Cr, Mo, N), offering better corrosion resistance and longer service life in aggressive environments. |
*Prices vary based on thickness, width, quantity, finish, and market conditions. Contact Huaxiao Metal for the most accurate quotation and available stock.
Key Takeaway:
Choose S31803 when you need good performance at a lower cost.
Choose S32205 when maximum corrosion resistance and durability justify the slightly higher price.
Typical Applications
Both S31803 and S32205 are widely used in industries that demand high corrosion resistance and high strength.
Common Applications
Oil & Gas Industry: offshore platforms, pipelines
Marine Engineering: seawater systems
Chemical Processing: heat exchangers, reactors
Desalination Plants: high‑pressure piping
Pressure Vessels & Storage Tanks
S32205 is often selected when the service environment is more aggressive or involves higher chloride exposure.
When to Choose S31803 vs S32205
| Situation | Better Option |
|---|---|
| General industrial corrosion resistance | S31803 |
| Harsh chloride / seawater environments | S32205 |
| Budget‑sensitive projects | S31803 |
| Maximum corrosion resistance | S32205 |
If your application involves severe corrosive media, high stress, or long service life requirements, S32205 is typically a more reliable choice — though both are excellent materials.
Material Standards & Specifications
Both S31803 and S32205 conform to:
✔ ASTM A240 – Stainless Steel Plate, Sheet, and Strip
✔ ASTM A276 – Stainless Steel Bars
✔ EN 1.4462 – Duplex Stainless Steel Grade
Standard products include:
- Plate
- Sheet
- Coil
- Bar
- Pipe
FAQ: S31803 Vs S32205
Are S31803 and S32205 interchangeable?
Yes — in many applications they can be, but S32205 generally offers higher corrosion resistance.
Can S31803 be used in seawater environments?
Yes, but S32205 is usually preferred due to its enhanced chloride resistance.
What is the main advantage of duplex stainless steel over 316L?
Duplex grades typically have higher strength and better stress corrosion cracking resistance.
Can I use S32205 if my design calls for S31803?
Yes. Since S32205 meets or exceeds all parameters of S31803, it is a superior substitute and is widely accepted by engineering standards worldwide.
Is there a price difference between S31803 and S32205?
Because S32205 has slightly more Molybdenum, its raw material cost is marginally higher. However, because it is now the industry standard, the market price is virtually the same due to mass production.
Huaxiao Metal | 2205 Duplex Stainless Steel Supplier
At Huaxiao Metal, we supply premium 2205 duplex stainless steels, including:
✔ S31803 Duplex Stainless Steel
✔ S32205 Duplex Stainless Steel
✔ Plate, Sheet, Coil, Bar, Pipe
We can provide:
Various thicknesses and widths
Surface finishes (2B, NO.1, pickled, polished)
Custom processing
Competitive factory pricing
Fast global delivery
📩 Contact us today to get the latest 2205 duplex stainless steel price and technical support.
