Why Is Duplex 2205 Used in Refinery Plate Heat Exchangers?

Duplex 2205 stainless steel is widely considered for refinery and petrochemical heat exchangers when conventional austenitic stainless steels do not provide enough margin against chloride-related localized corrosion or stress-corrosion cracking.

The material is particularly relevant when an exchanger combines thin metallic heat-transfer surfaces, welded fabrication, crevices, chloride-bearing cooling water and significant mechanical loading.

However, a request for “2205 heat exchanger material” is not a complete specification.

A pressed plate, a tubesheet, a heat-exchanger tube and a nozzle may all use Duplex 2205, but they require different raw-material forms and can fall under different ASTM product standards.

This guide connects:
heat exchanger component → corrosion environment → Duplex 2205 raw material → product standard → fabrication → inspection → RFQ.

Quick Answer: Where Does 2205 Fit in a Refinery Heat Exchanger?

Subject to the actual process chemistry, design temperature, pressure and project metallurgy specification, Duplex 2205 may be considered for:

• pressed plate heat-exchanger plates;
• all-welded plate packs;
• plate-and-shell heat-exchanger plates;
• tubesheets;
• heat-exchanger shells;
• channel components;
• heat-exchanger tubing;
• nozzles;
• selected piping connections;
• other chloride-exposed wetted components.

2205 should not be selected simply because an exchanger is installed in a refinery.

The design engineer should review both the process side and the cooling side before the alloy is specified.

Why Does Chloride Cooling Water Change Material Selection?

Cooling water is often one of the controlling environments in refinery heat-exchanger material selection.

Depending on location and water treatment, a cooling system can contain:

• chlorides;
• dissolved salts;
• oxygen;
• deposits;
• biofouling;
• crevice-forming solids;
• concentration effects during evaporation or shutdown.

These conditions can promote pitting, crevice corrosion and chloride stress-corrosion cracking in susceptible stainless steels.

Duplex 2205 contains chromium, molybdenum and nitrogen and has substantially better resistance to chloride stress-corrosion cracking than conventional 300-series austenitic stainless steels in many suitable environments.

This is one reason 2205 has been used in refinery and petrochemical heat exchangers exposed to chloride-bearing or brackish cooling water.

For broader refinery material selection, see:

JUDE Steel Duplex 2205 for Refineries & Chemical Plants
.

S32205 vs S31803: Which 2205 Should Buyers Specify?

“2205” is a commercial grade name rather than a complete UNS specification.

Two UNS designations are commonly associated with Duplex 2205:

Buyers should not assume that an order written as only “2205” automatically means S32205.

If the project requires S32205, state the UNS designation explicitly on the RFQ and purchase order.

Duplex 2205 Grade Designations and Product Standards

The product standard should follow the actual raw-material form.

A cold-rolled exchanger plate and a seamless exchanger tube should not be ordered under the same ASTM specification merely because both are Duplex 2205.

For JISCO JUDE’s broader duplex range, see:

Duplex Stainless Steel 2205, 2507, 2304 & 2101
.

ASTM A240 UNS S32205 Chemical Composition

The following values represent specified UNS S32205 chemistry limits commonly used for ASTM A240 flat products.
They should not be described as producer-specific typical chemistry.

The delivered heat should be verified against the applicable specification and Mill Test Certificate.

Which Heat Exchanger Components Use Duplex 2205?

1. Pressed Plate Heat-Exchanger Plates

Plate heat exchangers use thin corrugated metallic plates to create alternating flow channels.

These plates combine several demanding requirements:

• corrosion resistance;
• press-forming capability;
• thin-gauge dimensional control;
• surface quality;
• pressure resistance;
• repeatable plate geometry.

Where the process or cooling water contains significant chlorides, Duplex 2205 may provide a useful corrosion and strength margin compared with conventional 316L.

The required sheet thickness and cold-rolled surface should be defined by the heat-exchanger manufacturer.

JISCO JUDE publishes cold-rolled stainless steel sheet and coil in a general range of:

0.3–8.0 mm Cold-Rolled Stainless Steel Sheet & Coil
.

2. Welded Plate Packs

Some refinery heat exchangers use welded plate packs rather than gasketed plate assemblies.

In this configuration, material selection must account for both the base metal and welded zones.

Duplex welding requires control of:

• heat input;
• interpass temperature;
• shielding and backing gas;
• filler metal where used;
• cooling rate;
• weld cleanliness;
• final phase balance.

An acceptable base-metal MTC alone does not guarantee that the fabricated welded plate pack retains the required duplex corrosion and toughness properties.

3. Plate-and-Shell Heat Exchanger Components

Plate-and-shell exchangers combine a compact plate pack with a pressure-containing shell.

Depending on the project, Duplex 2205 can be evaluated for:

• heat-transfer plates;
• plate packs;
• shell components;
• nozzle reinforcements;
• selected pressure-retaining wetted parts.

The component drawing should identify which parts require S32205 rather than applying one alloy designation to the entire exchanger by default.

4. Tubesheets

Shell-and-tube heat exchangers may use Duplex 2205 tubesheets when chloride-bearing fluids or cooling water create a corrosion environment that justifies the grade.

Tubesheet procurement can require:

• ASTM A240 S32205 plate;
• plate thickness;
• diameter or rectangular blank size;
• UT where required;
• machining allowance;
• tube-hole pattern;
• surface condition;
• full heat-number traceability.

For heavier flat material, review:

JISCO JUDE Hot-Rolled Stainless Steel Sheet & Plate
.

5. Shells and Channel Components

Duplex 2205 plate may also be used for selected exchanger shells, heads and channel components when the corrosion and pressure design support the material.

Its high strength can offer design advantages, but a thinner wall should only be adopted after code calculations, corrosion allowance, fabrication minimums and structural requirements are reviewed.

6. Heat-Exchanger Tubes

For tubular exchanger designs, Duplex 2205 can be supplied as stainless tubing under an applicable duplex tubing specification such as ASTM A789/A789M when accepted by the project.

Tube RFQs should include:

• UNS designation;
• OD;
• wall thickness;
• length;
• seamless or welded construction;
• heat treatment;
• surface condition;
• NDE requirements;
• tube-end requirements;
• quantity.

7. Nozzles and Piping Connections

A Duplex 2205 exchanger can also require matching corrosion-resistant nozzles and piping connections.

Depending on component form, the system may include:

• ASTM A790 S32205 pipe;
• ASTM A182 F60 forged flanges;
• ASTM A815 WPS32205 butt-weld fittings.

The alloy family may be the same while the required material standards are different.

Component-to-Raw-Material Procurement Matrix

ASTM A240 vs A789 vs A790

ASTM A240/A240M

ASTM A240/A240M covers stainless steel plate, sheet and strip.

For a Duplex 2205 heat exchanger, it can apply to:

• pressed exchanger plates;
• tubesheets;
• shell plate;
• channel plate;
• fabricated flat components.

ASTM A789/A789M

ASTM A789/A789M covers seamless and welded ferritic/austenitic stainless steel tubing for general service where corrosion resistance, particularly resistance to stress-corrosion cracking, is important.

It can be relevant to Duplex 2205 exchanger tubing when specified by the equipment design.

ASTM A790/A790M

ASTM A790/A790M covers seamless and straight-seam welded ferritic/austenitic stainless steel pipe for general corrosive service.

It may be relevant to exchanger nozzles and connected Duplex 2205 process piping.

Purchasing rule:
select the material standard according to product form rather than using ASTM A240 for every component made from S32205.

Why Can Duplex 2205 Outperform 316L in Chloride Cooling Water?

Type 316L contains molybdenum and performs well in many process environments, but its resistance to chloride-induced localized corrosion and chloride stress-corrosion cracking can become limiting as chloride concentration, temperature and crevice severity increase.

Duplex 2205 contains higher chromium, molybdenum and nitrogen levels together with a duplex microstructure.

This can provide:

• higher pitting-resistance margin;
• better chloride SCC resistance;
• higher mechanical strength;
• potentially reduced material thickness where code design permits.

Industrial case histories have demonstrated successful use of Duplex 2205 in refinery plate air-cooler and plate-and-shell heat exchanger service.

Those case histories demonstrate technical feasibility but should not be interpreted as a universal lifetime guarantee for another refinery.

For technical background, see:

Outokumpu — Material Challenges of Plate Heat Exchangers
.

Why Does 2205 Not Automatically Mean Seawater Service?

“Chloride resistant” does not mean “unlimited seawater resistant.”

Localized-corrosion risk depends on:

• chloride concentration;
• temperature;
• oxygen;
• flow velocity;
• deposits;
• crevice geometry;
• biofouling;
• shutdown condition.

For warm seawater, severe crevices or more aggressive chloride service, Super Duplex 2507 or another higher-alloy material may require evaluation.

When Should 2507 Be Evaluated Instead of 2205?

A more highly alloyed material should be considered when service conditions exceed the practical corrosion margin of standard Duplex 2205.

Potential triggers include:

• higher chloride concentration;
• higher temperature;
• severe stagnant crevices;
• sour and highly contaminated refinery streams;
• aggressive acid/chloride combinations;
• customer specifications requiring super duplex.

2507 should not be described simply as a “better 2205.”
It brings greater corrosion resistance together with higher alloy cost and tighter fabrication requirements.

PREN: Useful Screening Tool, Not a Guarantee

Pitting Resistance Equivalent Number is commonly estimated as:

PREN = %Cr + 3.3 × %Mo + 16 × %N

S32205 commonly produces a PREN in the mid-30s.

PREN is useful when screening stainless steels for localized-corrosion resistance, but it does not include every factor that controls real exchanger performance.

It does not directly account for:

• surface condition;
• welding;
• crevice geometry;
• temperature;
• flow;
• biofouling;
• actual process chemistry.

Do not specify only:
“PREN >35.”

The actual UNS grade and material standard should remain on the purchase order.

Press Forming Duplex Heat Exchanger Plates

Pressed heat-exchanger plates contain complex corrugations and local strain concentrations.

Duplex 2205 has lower ductility than conventional austenitic grades such as 316L, so forming behavior must be considered during tooling and plate design.

Important controls can include:

• incoming sheet flatness;
• sheet thickness;
• tool geometry;
• forming strain;
• local thinning;
• surface damage;
• springback.

The exchanger manufacturer should qualify the forming route using its actual plate geometry rather than assuming that 316L forming parameters can be copied directly.

Welding and Duplex Phase Balance

Duplex stainless steel obtains its properties from a controlled balance of ferritic and austenitic phases.

Welding changes the local thermal history and can affect:

• ferrite/austenite balance;
• toughness;
• corrosion resistance;
• intermetallic-phase formation.

The welding procedure should therefore control heat input, interpass temperature, filler selection, shielding and cooling according to the applicable fabrication specification.

A fixed statement such as “2205 must contain exactly 50% ferrite and 50% austenite” is not appropriate as a generic acceptance requirement.

Phase-balance acceptance should follow the project, welding and equipment specification.

Why May ASTM A923 Be Specified?

Duplex stainless steels can form detrimental intermetallic phases if they experience unfavorable thermal exposure during production or fabrication.

ASTM A923 provides test methods intended to detect detrimental intermetallic phase to the extent that toughness and corrosion resistance are significantly affected.

The standard includes:

• Method A — sodium hydroxide etch examination;
• Method B — Charpy impact testing;
• Method C — ferric chloride corrosion testing.

ASTM A923 testing is not automatically required for every Duplex 2205 heat-exchanger order.

When required, the purchaser should state:

• applicable method;
• product or weld condition;
• sampling location;
• acceptance criteria;
• reporting requirement.

Official reference:

ASTM A923 — Detection of Detrimental Intermetallic Phase in Duplex Stainless Steel
.

Surface Condition, Pickling and Cleanliness

The corrosion performance of a heat exchanger is affected by more than alloy chemistry.

Fabrication specifications may control:

• surface contamination;
• embedded carbon-steel particles;
• weld discoloration;
• oxide scale;
• pickling;
• cleaning;
• surface defects.

Fabrication tools and handling areas should avoid uncontrolled carbon-steel contamination when the project requires corrosion-critical stainless equipment.

What Should a Duplex 2205 Heat Exchanger RFQ Include?

1. Exchanger type: gasketed PHE, welded PHE, plate-and-shell or shell-and-tube.
2. Component: plate, tubesheet, shell, tube, nozzle or flange.
3. Grade: Duplex 2205 / UNS S32205.
4. Material standard: ASTM A240, A789, A790, A182 or project specification.
5. Dimensions: sheet thickness, plate thickness, OD, wall, width and length.
6. Process-side medium: identify composition.
7. Cooling-side medium: cooling water, brackish water or other fluid.
8. Chloride concentration: normal and maximum where available.
9. Operating temperature: both sides.
10. Design temperature: both sides where required.
11. Operating pressure: both sides.
12. Design pressure: where applicable.
13. pH: where relevant.
14. H2S / sour condition: where relevant.
15. Forming: plate pressing requirement.
16. Welding: applicable WPS/project requirement.
17. ASTM A923: method and acceptance criteria if required.
18. PMI: required or not required.
19. NDE: PT, UT or other project requirements.
20. Certificate: EN 10204 3.1, 3.2 or project requirement.
21. Quantity: sheets, plates, tubes or total tonnage.
22. Drawing: exchanger or component drawing.
23. Destination: country, port and required delivery date.

Example Duplex 2205 Plate Heat Exchanger RFQ

Incoming Inspection

Depending on project requirements, incoming Duplex 2205 heat-exchanger material may be checked for:

• UNS designation;
• heat number;
• Mill Test Certificate;
• Cr, Mo and N chemistry;
• mechanical properties;
• sheet or plate thickness;
• flatness;
• surface condition;
• tube OD and wall thickness;
• PMI;
• UT or NDE where specified;
• ASTM A923 results where required;
• full traceability.

PREN calculations or nominal alloy names should not replace verification of the actual heat chemistry and governing material specification.

How JISCO JUDE Supports Heat Exchanger Manufacturers

JISCO JUDE supplies stainless steel flat products for refinery, petrochemical, chemical-processing and heat-exchanger manufacturers.

Relevant JISCO JUDE resources include:

• Duplex Stainless Steel 2205 & 2507
• Cold-Rolled Stainless Steel Sheet & Coil
• Hot-Rolled Stainless Steel Sheet & Plate
• Cutting, Slitting & Cut-to-Length Services

Additional JUDE Steel references:

• Duplex 2205 Grade Page
• Stainless Steel Sheet & Plate
• Processing Services & Capabilities

Specific S32205 thickness, surface, forming quality, plate size, tube availability, inspection and certification should be confirmed for each project.

Frequently Asked Questions

Why is Duplex 2205 used in some refinery heat exchangers?

2205 combines high mechanical strength with strong resistance to chloride stress-corrosion cracking and localized corrosion, making it useful in selected exchangers exposed to chloride-bearing cooling water or corrosive refinery streams.

Should I order S32205 or S31803?

S32205 is commonly preferred for modern Duplex 2205 procurement because it specifies tighter minimum chromium, molybdenum and nitrogen contents. Follow the exact UNS designation required by the project.

Can Duplex 2205 replace 316L in every heat exchanger?

No. Material selection depends on corrosion environment, temperature, pressure, fabrication, formability and cost. 316L may remain adequate in less demanding environments and is generally easier to form.

Is Duplex 2205 suitable for seawater heat exchangers?

Not automatically. Seawater suitability depends on temperature, crevices, flow, fouling and other conditions. More severe seawater service may require Super Duplex 2507 or another higher-alloy material.

When should 2507 be considered instead of 2205?

2507 should be evaluated when chloride concentration, temperature, sour contamination, crevice severity or project corrosion requirements exceed the practical margin of standard Duplex 2205.

Does PREN guarantee heat-exchanger corrosion resistance?

No. PREN is a useful alloy-screening parameter, but actual performance also depends on welding, surface condition, crevices, process chemistry, temperature and flow conditions.

Is ASTM A923 testing mandatory for every 2205 exchanger?

No. ASTM A923 testing should be specified when required by the purchaser, equipment specification or project metallurgy requirements. The required test method and acceptance criteria should be stated in the RFQ.

Should I specify ASTM A240 or ASTM A789?

ASTM A240 applies to plate, sheet and strip. ASTM A789 applies to ferritic/austenitic stainless tubing. The correct specification depends on the actual exchanger component being purchased.

Why is welding control important for Duplex 2205?

Duplex properties depend on a suitable ferrite-austenite balance. Uncontrolled welding thermal cycles can affect phase balance, corrosion resistance, toughness and the formation of detrimental intermetallic phases.

What should I send JISCO JUDE for a Duplex 2205 heat-exchanger quotation?

Send the exchanger/component drawing, UNS grade, ASTM specification, dimensions, process and cooling media, chloride concentration, operating temperature and pressure, forming and welding requirements, inspection requirements, quantity and destination.

Request Duplex 2205 Material for Refinery Heat Exchangers

Technical note:
This article is intended for preliminary material screening and raw-material procurement guidance. Final Duplex 2205 heat-exchanger selection should be confirmed by the responsible equipment designer or materials engineer based on actual process chemistry, chloride concentration, temperature, pressure, crevice conditions, heat-transfer design, fabrication procedure, welding qualification and applicable construction code.