Our Duplex Stainless Steel Bolts deliver double the strength of 316 SS while resisting chloride attacks. With 22% chromium, 5% nickel, and 3% molybdenum (per ASTM A276), they achieve PREN values >35 - proven to withstand 100,000+ ppm chlorides in ASTM G48 testing.
Cold-forged heads provide 750 MPa tensile strength (exceeding ASME SA320 L43 requirements), perfect for offshore platforms where salt spray kills standard bolts. Third-party reports show <0.01mm/year pitting in seawater at 30°C. You'll get 2x the lifespan of 316 fasteners in chemical processing plants while saving 25% versus super duplex options.
We offer two finishes: passivated (per ASTM A967) to boost corrosion resistance, creating a 7-9μm oxide layer, and sandblasted (Ra 25-50μm) for better paint adhesion in outdoor projects. The passivation process removes free iron, making them 35% more resistant to chloride corrosion than untreated bolts.
As a Chinese manufacturer with 10 years supplying EU offshore and chemical industries, we run 5 duplex-specific cold heading lines and 7 thread rollers, producing 3,800 tons annually. Our raw material undergoes a special annealing process to maintain the 50-50 ferrite/austenite balance, checked via our in-house magnetic tester (accuracy ±1%).
We keep 220-350 tons in stock at our Qingdao warehouse, covering sizes from ¼" to 2" and lengths 1" to 20". Inventory updates in real time on our website, and FOB Qingdao shipments for in-stock bolts leave within 5 days-handy when your customers need to keep projects on schedule.
Orders over 45 tons get a 5.5% discount, plus free passivation and 15% of sea freight.
Here's our guarantee: If any Duplex Stainless Steel Bolts fail to meet ASTM A193 mechanical standards or show pitting corrosion within 8 years, we'll replace them within 6 days and refund all shipping costs. We also offer a 35-day price lock on confirmed orders, with a 2% repeat order discount for clients who reorder within 3 months.
Super Duplex Stainless Steel S31803 (UNS S31803; equivalent to 2205, DIN 1.4462)
Chemical Composition
Cr: 21.0-23.0%, Ni: 4.5-6.5%, Mo: 2.5-3.5%, N: 0.08-0.20%, C: ≤0.03%, Mn: ≤2.0%, Si: ≤1.0%, P: ≤0.03%, S: ≤0.02%
Mechanical Properties
Tensile Strength: ≥690 MPa
Yield Strength: ≥450 MPa
Hardness: ≤290 HB (Brinell); ≤31 HRC (Rockwell)
Elongation: ≥25%
Corrosion Resistance
Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride-rich environments (e.g., seawater, brines). Superior to 316/316Ti in harsh chemicals.
Temperature Range
Continuous service: -50°C to 250°C (limited by ductility at high temperatures); ideal for subsea and offshore environments.
Magnetic Property
Magnetic (due to duplex microstructure: austenite + ferrite)
Metric Size (M)
Thread Pitch (mm)
Hex Head Width (mm)
Hex Head Height (mm)
Length Range (mm)
Imperial Equivalent
Thread Type (Imperial)
UNC (3/16"-24), UNF (3/16"-32)
UNC (5/16"-18), UNF (5/16"-24)
UNC (3/8"-16), UNF (3/8"-24)
UNC (1/2"-13), UNF (1/2"-20)
UNC (5/8"-11), UNF (5/8"-18)
Standard Compliance
Key Applications
ASTM A193 B8S, ISO 4017, DIN 933
Offshore oil and gas platforms (subsea pipelines, wellheads)
Desalination plants (reverse osmosis systems)
Chemical processing (acids, chlorides, and corrosive slurries)
Marine engineering (ship hulls, propeller shafts)
Pulp and paper industry (bleaching systems with chlorine compounds)
S31803 (2205)
High (yield strength 2× that of 316Ti)
Chloride Resistance
Excellent (resists seawater/SCC)
Good (but limited in high chloride levels)
Weldability
Good (requires controlled heat input to avoid ferrite/austenite imbalance)
Higher (premium for duplex microstructure)
Frequently Asked Questions
Q: What is your policy for product returns or replacements?
A: If products have quality issues caused by us, we'll arrange replacements or refunds within 30 days of receipt.
Q: Can you provide a certificate of origin (CO) for customs clearance?
A: Yes, we can provide CO, as well as other documents like commercial invoices and packing lists required for customs.
Q: How can we track the shipment after it's dispatched?
A: We'll provide a tracking number and logistics platform information once the shipment departs, so you can check the status in real time.
Q: Do you offer technical support for product installation or usage?
A: Yes, our technical team can provide installation guides, video tutorials, or even on-site support if needed.
