Alloys with the UNS numbers S31803 and S32205 have more traits of similarity than those of difference. They have a comparatively similar elemental composition. They are also both stainless steels. Moreover, they are both members of the same Duplex 2205 family. This means that even their austenite and ferrite contents are very similar to each other. Vishal Tube is a top-notch supplier and manufacturer of UNS numbers S31803 and S32205. We have crafted this guide to help you distinguish UNS S32205 vs S31803. This article about the difference between S32205 and S31803 is backed by years of experience and technical knowledge. It will also contain a duplex steel grades comparison of S32205 and S31803, and their chemical and mechanical composition.
What is UNS S32205?
UNS S31803 is an enhanced version of UNS S31803. It has the following characteristics:
- A more regulated chemical composition
- Provides better resistance to pitting
- Helps to avoid cracking
- Fights stress-related corrosion
What is S31803?
UNS S31803 is an improved variant of S32205 and has a more regulated chemical structure that leads to better resistance to chipping, breaking, and corrosion due to stress.
What are the mechanical properties of UNS S32205 vs S31803?
| Property | UNS S31803 | UNS S32205 |
| Tensile Strength | ~620 MPa min | ~620 MPa min |
| Yield Strength 0.2% Proof (MPa) | ~450 MPa min | ~450 MPa min |
| Elongation (%) | ≥25% | ≥25% |
| Hardness (Brinell, HB) | ≤293 HB | ≤293 HB |
| Impact Toughness (Charpy V-notch) | High (even at –50 °C) | Slightly higher and more stable at low temps |
| Fatigue Strength | Excellent | Excellent to slightly better |
| Corrosion Fatigue Resistance | Very good | Very good to excellent |
What are the Chemical properties of UNS S32205 vs S31803?
| Element | UNS S31803 | UNS S32205 | Difference |
| Carbon or C | ≤ 0.030 | ≤ 0.030 | Same—both have low carbon to reduce carbide precipitation and improve weldability. |
| Chromium or Cr | 21.0 – 23.0 | 22.0 – 23.0 | S32205 usually has slightly higher chromium, giving better pitting resistance. |
| Nickel or Ni | 4.5 – 6.5 | 4.5 – 6.5 | Same range – improves toughness and corrosion resistance. |
| Molybdenum or Mo | 2.5 – 3.5 | 3.0 – 3.5 | S32205 has slightly higher Mo for improved resistance to chloride-induced corrosion. |
| Manganese or Mn | ≤ 2.00 | ≤ 2.00 | Same—helps improve hot working properties. |
| Silicon or Si | ≤ 1.00 | ≤ 1.00 | Same—improves oxidation resistance. |
| Phosphorus or P | ≤ 0.030 | ≤ 0.030 | Same—kept low to maintain ductility and toughness. |
| Sulfur or S | ≤ 0.020 | ≤ 0.020 | Same—low sulfur to avoid hot cracking and maintain corrosion resistance. |
| Nitrogen or N | 0.08 – 0.20 | 0.14 – 0.20 | S32205 has slightly higher nitrogen for better pitting and crevice corrosion resistance. |
| Iron or Fe | Balance | Balance | Base element in both grades. |
What are the ideal applications of UNS S32205?
Offshore and Marine Industries
The parts are used in:
- Shipbuilding
- Hull structures
- Seawater pipes
- Propeller shafts.
Resistance to stress corrosion cracking and seawater corrosion is essential for offshore platforms and rigs, which is possible through UNS S32205.
Desalination facilities for:
- Evaporators
- Heat exchangers
- High-pressure pipes.
- The Petrochemical, Oil, and Gas Industry
- Pipeline systems for the transportation of:
- Chemical fluids
- Natural gas
- Crude oil
- Heat exchangers in settings with high chloride levels.
- Corrosive chemical storage tanks and pressure vessels.
- Equipment for deep-water operations.
3. The Fertilizer and Chemical Processing Sector
- Tanks, pipelines, and reactors that deal with caustic solutions, acids, and chlorides.
- Absorbers and scrubbers are used in devices that desulfurize flue gases.
- Agitators and mixers for corrosive media.
4. Paper and Pulp Sector
- Washers, bleaching machines, and digesters that deal with liquids that contain acid and chloride.
- Evaporators for black liquor and other equipment used in high-stress processes.
5. Generation of Power
- Cooling water systems in thermal and nuclear power facilities.
- Feedwater heaters and condensers that run in brackish or saltwater conditions.
What are the perfect applications of S31803?
1. Offshore and Marine Engineering
- FPSOs
- Offshore rigs,
- Ships’ seawater piping systems
- Seawater intake screens
- Maritime fasteners
- Propeller shafts
- Desalination facilities for pipe
- Brine heaters
- Evaporators
2. Petrochemical, Gas, and Oil Industries
- Subsea umbilicals
- Risers
- Flowlines in offshore oil fields
- Heat exchangers that deal with fluids high in chloride.
- Storage tanks and pressure vessels for storing chemicals or sour gases.
- Equipment used in refineries is subjected to elevated levels of hydrogen sulfide and chloride.
3. Processing of Chemicals: Acid, chloride, and caustic storage tanks, pipes, and reactors
4. Scrubbers and absorbers for flue gases
5. Combining machinery with strong chemical solutions.
Factors Influencing Grade Selection
For optimum performance, it is important to choose the right quality of duplex stainless steel. Selecting the ideal grade depends on a number of factors like the following:
- Maintenance demands
- Manufacturing technique
- Integration
- Pricing considerations,
- Environmental surroundings
- Industrial cionditions
- Application criteria.
The table below will help you understand the difference between S32205 and S31803 and make the best choice for your project:
| Factor | Go for S32205 | Go for S31803 |
| Corrosion level | Very high chloride, offshore, sour service | Moderate chloride, inland, low salinity |
| Budget | Less concern about cost | Need a cost-effective option |
| Standards | New projects, NORSOK compliance | Legacy projects, replacement parts |
| Service life | Long-term, maintenance-free | Short-term or replaceable equipment |
| Welding | Controlled process, skilled welders | Simpler fabrication environments |
Conclusion
Despite having very comparable compositions, nearly identical chemical and mechanical qualities, and membership in the same Duplex 2205 family. When you examine the difference between S32205 and S31803, you will find that UNS S32205 performs slightly better than S31803 due to minor variations in alloy concentration, especially in the areas of nitrogen, molybdenum, and chromium.
In reality, when you make the decision on UNS S32205 vs S31803, the decision process frequently boils down to industry requirements, financial constraints, and environmental harshness. S32205 is frequently the safest long-term option for new projects and demanding chemical processing, petrochemical, or maritime applications. S31803 can provide outstanding performance at a reasonable cost for inland applications, moderate chloride exposure, or replacing old equipment.
Vishal Tube is a supplier of both grades of duplex stainless steel, S31803 and S32205. We completely understand the difference between S32205 and S31803 and other duplex steel grade comparisons. Therefore, our products are dependable, strong, and resistant to corrosion. They are thoroughly inspected, and this ensures that they meet the efficiency requirements to have various types of industrial operations in a variety of sectors and different types of small and large units. We provide complete support in the selection of the appropriate grade that will guarantee your project’s best performance, longevity, and cost-effectiveness.