1. Composition
2205 Duplex: Contains ~22% chromium (Cr), 5-6% nickel (Ni), 3-3.5% molybdenum (Mo), and 0.14-0.22% nitrogen (N). Higher Cr, Mo, and N enhance corrosion resistance and strength.
316/316L: Contains ~16-18% Cr, 10-14% Ni, 2-3% Mo, and negligible nitrogen. Relies on higher Ni for basic corrosion resistance.
2. Microstructure
2205: Has a dual-phase structure (50% austenite + 50% ferrite), combining the ductility of austenite with the strength of ferrite.
316: Has a single-phase austenitic structure, making it more ductile and non-magnetic.
3. Mechanical Properties
Strength:
2205 has twice the yield strength (≥450 MPa) of 316 (≥205 MPa) and higher tensile strength (≥620 MPa vs. ≥515 MPa).
316 is more ductile with higher elongation (40-60% vs. 25-30% for 2205).
Hardness: 2205 (250-300 HB) is harder than 316 (150-200 HB).
Magnetism: 2205 is magnetic (due to ferrite), while 316 is non-magnetic.
4. Corrosion Resistance
General Corrosion: Both resist oxidation, but 2205 outperforms 316 in harsh environments.
Chloride Resistance:
2205 resists pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride-rich environments (e.g., seawater, brine up to ~3,000 ppm Cl⁻).
316 is vulnerable to SCC in high-chloride conditions (e.g., >300 ppm Cl⁻) and is used in less aggressive settings like food processing.
5. Applications
2205: Used in high-stress, corrosive environments such as offshore oil/gas, desalination plants, chemical tanks, and marine equipment.
316: Common in general-purpose applications like pharmaceutical equipment, architectural trim, and food/beverage processing.
6. Cost and Availability
2205 is more expensive due to higher alloy content and complex production. It's less widely available and may require custom orders.
316 is more cost-effective and readily available, making it a standard choice for many industries.
