Choosing the wrong stainless steel grade can mean premature corrosion failure, unexpected maintenance costs, or paying for performance you don’t need. This guide compares 304, 316, and duplex (2205/2507) grades across composition, strength, corrosion resistance, and cost — with clear recommendations for common applications.
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Quick Answer
For general-purpose applications, 304 is the cost-effective default. Choose 316 when chlorides, salt water, or mild acids are present. Choose duplex 2205 when you need both high strength and chloride corrosion resistance — it’s 2x stronger than 316L and often cheaper per unit of strength. Reserve super duplex 2507 for the most aggressive environments like offshore oil and gas. When in doubt, consult a materials engineer before specifying.
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Grade Overview: What Makes Each Different
304: The Workhorse
304 is an austenitic stainless steel containing 18-20% chromium and 8-10.5% nickel. It accounts for over 50% of global stainless steel production and is the default choice for indoor, non-corrosive applications.
Strengths: Excellent formability, good corrosion resistance, widely available, lowest cost
Weaknesses: Susceptible to pitting corrosion in chloride environments, not suitable for marine use
316/316L: The Marine Grade
316 adds 2-3% molybdenum to the 304 composition, dramatically improving pitting and crevice corrosion resistance. 316L is the low-carbon variant (≤0.03% C) optimized for welding applications.
Strengths: Superior chloride corrosion resistance, good weldability (316L), food and pharmaceutical grade
Weaknesses: 50-55% more expensive than 304, still vulnerable to stress corrosion cracking above 60°C in chlorides
Duplex 2205: The High-Strength Hybrid
Duplex 2205 (UNS S32205) has a mixed microstructure of roughly 50% austenite and 50% ferrite, combining strengths of both phases. It contains 22% chromium, 5-7% nickel, and 3% molybdenum.
Strengths: Yield strength 2x that of 316L, excellent stress corrosion cracking resistance, lower nickel content than 316
Weaknesses: More difficult to weld, reduced toughness at very low temperatures, less widely stocked
Super Duplex 2507: The Extreme Environment Grade
Super duplex 2507 (UNS S32750) pushes chromium to 25% and molybdenum to 4%, delivering the highest corrosion resistance among standard stainless grades.
Strengths: Exceptional pitting resistance (PREN >42), high strength, seawater compatible
Weaknesses: 2.5-3x the cost of 304, limited availability in all product forms, demanding fabrication requirements
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Chemical Composition Comparison
Grade | Cr (%) | Ni (%) | Mo (%) | C (%) | N (%) | PREN
304 | 18-20 | 8-10.5 | — | ≤0.08 | — | 18-20
316L | 16-18 | 10-14 | 2-3 | ≤0.03 | — | 22-26
2205 | 22-23 | 4.75-6.5 | 3-3.5 | ≤0.03 | 0.14-0.20 | 34-38
2507 | 24-26 | 6-8 | 3-5 | ≤0.03 | 0.24-0.32 | 42+
Note: PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3×(%Mo + 0.5×%N). Higher PREN = better pitting resistance. A PREN above 32 is generally required for seawater service.
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Mechanical Properties Comparison
Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Hardness (HB)
304 | 205 | 520 | 40 | 201
316L | 170 | 485 | 40 | 217
2205 | 450 | 620 | 25 | 293
2507 | 550 | 795 | 15 | 310
Key takeaway: Duplex grades deliver roughly double the yield strength of austenitic grades. This means you can often use thinner material for the same load-bearing capacity — a 3mm 2205 sheet can replace a 6mm 316L sheet in structural applications, offsetting the higher per-kg cost.
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Corrosion Resistance: Which Grade Survives Your Environment?
Pitting Corrosion Resistance (Chloride Environments)
Environment | 304 | 316L | 2205 | 2507
Indoor / dry | Excellent | Excellent | Excellent | Excellent
Urban outdoor | Good | Excellent | Excellent | Excellent
Coastal / marine | Poor | Fair | Excellent | Excellent
Chemical processing | Poor | Good | Excellent | Excellent
Offshore oil & gas | Not recommended | Fair | Good | Excellent
Stress Corrosion Cracking (SCC)
Austenitic grades (304, 316) are vulnerable to chloride stress corrosion cracking above 60°C. Duplex grades resist SCC up to 150-200°C, making them mandatory for hot chloride applications like heat exchangers and hot water systems.
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Cost Comparison (FOB Shanghai, Q3 2026)
Grade | Product Form | Price (USD/ton) | Relative Cost | Cost per MPa of Yield Strength
304 | Cold rolled sheet (2B) | $2,255 – $2,480 | 1.0x | $11.0
316L | Cold rolled sheet (2B) | $3,410 – $3,680 | 1.55x | $20.1
2205 | Cold rolled plate | $4,200 – $4,600 | 1.90x | $9.3
2507 | Cold rolled plate | $6,800 – $7,400 | 3.10x | $12.4
Important insight: While duplex 2205 costs 90% more than 304 per ton, its double yield strength means the cost per unit of structural strength is actually lower. For load-bearing applications, 2205 can be the most economical choice despite the higher per-kg price.
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Application Selection Guide: Which Grade Should You Choose?
Choose 304 if your application involves:
• Indoor architectural elements and decorative trim
• Food processing equipment (dry environment)
• Kitchen appliances and cookware
• General-purpose sheet metal work
• Budget-constrained projects with no chloride exposure
Choose 316/316L if your application involves:
• Marine and coastal structures (mild exposure)
• Chemical storage tanks (mild acids)
• Pharmaceutical and food-grade piping
• Outdoor architectural features in polluted urban areas
• Welded constructions (choose 316L for its lower carbon)
Choose Duplex 2205 if your application involves:
• Heat exchangers with chloride-bearing water
• Pressure vessels requiring high strength
• Chemical tankers and processing equipment
• Bridge components in de-icing salt environments
• Desalination plant equipment
Choose Super Duplex 2507 if your application involves:
• Offshore oil and gas platforms
• Seawater handling systems
• Flue gas desulfurization equipment
• High-chloride chemical processing
• Downhole oil and gas tools
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Common Mistakes to Avoid
Mistake 1: Over-specifying 316 when 304 works
Many buyers default to 316 “to be safe,” but for indoor or dry environments, 304 provides identical service life at 35% lower cost. Reserve 316 for applications where chlorides are actually present.
Mistake 2: Ignoring duplex for high-strength applications
When structural strength matters, specifying 316L at 6mm thickness when 2205 at 3mm would suffice is a costly error. The material cost savings can reach 30-40% even though 2205 costs more per kg.
Mistake 3: Welding duplex without proper procedure
Duplex requires controlled heat input and nitrogen backing gas during welding. Improper welding can shift the phase balance and causepremature corrosion. Always use weldersqualified for duplex fabrication.Mistake 4: Using 316 in hot chloride service316L is vulnerable to stress corrosion crackingabove 60°C in chloride environments. For hotwater, brine, or coastal heat exchangers, switchto duplex 2205 to avoid catastrophic failure.
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Frequently Asked Questions
Q: Is duplex stainless steel magnetic?
Yes. Unlike austenitic grades (304, 316) whichare generally non-magnetic, duplex grades aremagnetic due to their ferrite content. This isnormal and does not indicate a quality problem.
Q: Can I weld 304 to 316?
Yes, you can weld 304 to 316 using 308L or309L filler metal. The joint will have corrosionresistance closer to 304. This is common inmixed-grade fabrication but ensure the fillermetal is appropriate for the service environment.
Q: Why is duplex 2205 sometimes cheaper than 316L?
Duplex contains only 5-7% nickel versus 316’s 10-14%. Since nickel is the most volatile cost component in stainless steel, lower nickelcontent can make 2205 less expensive than316L during periods of high nickel prices. As ofQ3 2026, 2205 remains slightly more expensiveper kg but offers better value per unit of strength.
Q: What is the temperature limit for each grade?
304 and 316: -196°C to 800°C (oxidizingenvironment). Duplex 2205: -50°C to 300°C(avoid prolonged use above 300°C due to 475°Cembrittlement). Super duplex 2507: -50°C to250°C. For high-temperature applications above800°C, consider 309 or 310 austenitic grades.
Q: How do I know if I need super duplex 2507 instead of 2205?
The key indicator is the PREN value. If yourenvironment has a chloride content equivalentto full seawater at elevated temperature, youneed a PREN above 40 – that means 2507. For
most industrial chloride exposure, 2205 (PREN34-38) is sufficient. When unsure, request acorrosion testing consultation.
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Need Help Selecting the Right Grade for Your Project?
Our technical team has 15+ years of experiencehelping clients in 68 countries select the mostcost-effective stainless steel grade for theirspecific application. We stock 304, 316L, 2205,and 2507 in sheet, plate, coil, bar, and pipe forms.
Send us your application details and operating environment – we’ll recommend the optimal grade and provide a quotation within 24 hours.
Request a Grade RecommendationCWhatsApp:+86-15365266939 zyta@huaxinmetal.com
Prices referenced are FOB Shanghai, Q3 2026.All technical data based on ASTM A240 and EN10088 standards. Consult our engineers forapplication-specific verification.
Author: JiangsSu Hua Steel Technical Team – 15 years of stainless steel manufacturing and exportexperience. ISO 9001:2015 certified. Productstested per ASTM, BS EN, and DIN standards. X-
ray fluorescence inspection on every order.
