Selection summary
Overview
2507 super duplex stainless combines approximately 25% chromium with molybdenum and nitrogen to provide very high strength and high resistance to chloride pitting, crevice corrosion, and stress-corrosion cracking. It is used in demanding offshore, desalination, chemical, and pulp systems, but welding, phase balance, temperature limits, sour-service rules, and exact product standards remain decisive.
This page separates standard-oriented limits from typical reference data. Purchase acceptance comes from the ordered specification and certified material test report.
Names and systems
Identity & standards
Similar designations across ASTM, EN, JIS, and other systems are not automatically interchangeable. Product form and ordered standard control chemistry, properties, dimensions, condition, and testing.
Reference chemistry
Composition
| Element | Reference range | Why it matters |
|---|---|---|
| Chromium | 24.0–26.0% | Passive-film strength and duplex balance |
| Nickel | 6.0–8.0% | Austenite balance and toughness |
| Molybdenum | 3.0–5.0% | Pitting and crevice resistance |
| Nitrogen | 0.24–0.32% | Strength, pitting resistance, and phase balance |
Concise grade-family reference only. Confirm every element limit against the current standard for the exact product ordered.
Condition matters
Reference properties
Solution-annealed reference; product form and specification control
Solution-annealed flat-product reference with thickness limits
Typical room-temperature engineering reference
Environment first
Corrosion behavior
Provides substantially greater chloride pitting and crevice resistance than 2205 in many correctly controlled environments.
It is not immune to hot seawater crevices, deposits, galvanic effects, sour-service cracking, or fabrication damage; environment-specific qualification remains necessary.
Temperature, concentration, deposits, crevices, stress, surface finish, cleaning, and fabrication quality can change service performance.
Service limits
Temperature & service
Phase stability and code toughness limits constrain elevated and low-temperature service; do not extrapolate room-temperature data.
Delivery condition
Heat treatment & condition
2507 requires tightly controlled solution annealing and rapid cooling to achieve the intended phase balance and avoid intermetallic phases.
It is not hardened by thermal treatment; welding, hot forming, repair, and postweld exposure must limit heat input, interpass temperature, oxidation, nitrogen loss, and harmful phase formation.
Process route
Fabrication
High strength increases forming loads and springback; machining needs rigid setup and controlled parameters.
Welding must control heat input, interpass temperature, filler, shielding, phase balance, harmful phases, and postweld surface condition.
Magnetic response: Magnetic because of its duplex structure.
Decision boundaries
Comparisons & substitution
2507 offers higher strength and substantially more chloride pitting/crevice margin than 2205, but costs, forming loads, machining, welding control, and availability are more demanding.
6% molybdenum austenitic or nickel alloys may be preferred for specific acid, fabrication, temperature, or phase-stability requirements; PREN alone does not decide substitution.
Where it is used
Applications
Ordering scope
Product forms & standards
Plate, sheet, and strip in the specified solution-annealed condition with the exact UNS designation and any ordered corrosion testing.
Pipe, tube, fittings, flanges, bar, and forgings under form-specific standards with heat treatment, weld, phase-balance, and NDE controls.
Decision support
Selection guidance
Choose this grade when
- Severe chloride exposure requires more pitting and crevice margin than 2205 can demonstrate.
- High strength and corrosion resistance can be qualified together under the governing code and product standard.
Review another grade when
- The fabricator cannot control duplex welding, ferrite balance, intermetallic phases, and cleaning.
- Service includes sour conditions, extreme temperature, or crevices outside documented qualification.
Before ordering
Procurement checklist
Name the governing product specification and edition, exact UNS designation, dimensions, tolerances, finish, and delivery or heat-treatment condition.
Require a traceable material test report and verify chemistry, mechanical tests, heat treatment, marking, and any supplementary examination against the purchase order.
State the service environment, design temperature, fabrication route, inspection plan, certification, packaging, and any regulatory or end-user approval before order release.
Traceable evidence