ASTM A790 Duplex 2205 Seamless Pipe with Chloride & Stress Corrosion Cracking Resistance and Ferrite-Austenite Microstructure in Solution Annealed Condition

ASTM A790 UNS S32205 / S31803 Duplex 2205 Seamless Pipe is a ferritic-austenitic duplex stainless steel pipe designed for corrosive process environments where a combination of corrosion resistance and higher mechanical strength is required.

Commonly known as Duplex 2205, the material is based on a two-phase austenitic-ferritic microstructure. UNS S32205 is the commonly specified 2205 composition, while UNS S31803 represents the earlier standard duplex composition. Both designations are closely associated with the 2205 material family.

Manufactured according to ASTM A790 / ASME SA790, the seamless pipe is suitable for pressure-containing piping systems exposed to general corrosive service, chloride-containing environments and selected process media. ASTM A790 covers seamless and straight-seam welded ferritic/austenitic stainless steel pipe with particular emphasis on corrosion resistance and stress corrosion cracking resistance.

• Austenitic-Ferritic Duplex Structure: Duplex 2205 combines austenitic and ferritic phases, giving the material a different balance of strength and corrosion resistance from conventional austenitic stainless steels.
• Chloride Corrosion Resistance: The chromium, molybdenum and nitrogen alloying system provides resistance to localized corrosion in many chloride-containing environments.
• Stress Corrosion Cracking Resistance: Duplex 2205 is commonly selected where chloride stress corrosion cracking is an important material-selection consideration.
• Higher Yield Strength: Compared with conventional 300-series austenitic stainless steels, Duplex 2205 provides substantially higher yield strength, which can be advantageous in pressure-containing piping design.

UNS S31803 and UNS S32205 should not simply be treated as two unrelated grades.

The narrower and higher minimum alloying ranges of S32205 provide more defined corrosion-resistance requirements than the original S31803 composition.

• Duplex Microstructure: The two-phase structure provides a balance between austenitic toughness and ferritic strength.
• Corrosion-Oriented Material Selection: 2205 is widely considered for process environments involving chlorides, seawater exposure and aggressive industrial media.
• High Mechanical Strength: Its higher yield strength can provide an advantage in pressure piping design compared with many conventional austenitic grades.
• Seamless Construction: The seamless manufacturing route eliminates a longitudinal weld seam and is suitable for pressure-containing pipe applications.
• Process Piping Compatibility: ASTM A790 2205 pipe is commonly specified for chemical, petrochemical, oil and gas, marine and pollution-control systems.

Rather than using only broad terms such as "industrial use," this product is better positioned around specific service environments:

• Chemical Process Piping
• Petrochemical Process Lines
• Oil & Gas Piping
• Offshore Piping Systems
• Seawater Service
• Desalination Systems
• Marine Piping
• Chloride-Containing Process Lines
• Pollution Control Equipment
• Pulp & Paper Processing
• Chemical Storage and Transfer Systems

• Process Piping Systems
• Offshore Piping Modules
• Seawater Piping
• Desalination Equipment
• Chemical Process Units
• Oil & Gas Production Equipment
• Heat Exchanger Piping
• Pumps and Process Skids
• Pollution Control Systems
• Storage and Transfer Equipment

A typical seamless pipe manufacturing route includes:

1. Billet Preparation
2. Hot Piercing
3. Hot Rolling or Extrusion
4. Cold Finishing Where Required
5. Solution Annealing
6. Pickling / Surface Treatment
7. Straightening
8. Cutting
9. Dimensional Inspection
10. Hydrostatic or Nondestructive Testing
11. Final Inspection
12. Marking and Packaging

Typical inspection points include:

• Outside Diameter
• Wall Thickness
• Ovality
• Straightness
• Length
• End Squareness
• Surface Condition
• Pipe Weight

Pipe dimensions can be supplied according to the applicable dimensional standard and project specification.

Available inspection may include:

• Chemical Composition Analysis
• Tensile Test
• Yield Strength Test
• Elongation Test
• Hardness Test
• Flattening Test
• Hydrostatic Test
• Eddy Current Testing
• Ultrasonic Testing
• PMI
• Dimensional Inspection
• Surface Inspection
• Ferrite / Phase Balance Examination
• Corrosion Testing Where Required
• Heat Treatment Record

ASTM A790 includes requirements for tensile testing, hardness, flattening, hydrostatic testing and nondestructive electric testing.

For duplex stainless steel, the ferrite-austenite balance is an important quality characteristic. Depending on the project specification, additional metallographic examination may be performed to verify the duplex microstructure after solution annealing.

This can be particularly relevant for applications involving:

• Chloride Service
• Offshore Systems
• Seawater
• Pressure Piping
• Welded Components