Heat Exchanger Tube Materials: Complete Selection Guide

Quick Answer

Heat exchanger tube material selection determines service life, capital cost, and operating cost over a 20-30 year exchanger life. The four primary material families are: carbon steel (A179, A192, A210 — lowest cost, fresh water and clean hydrocarbon service to 400°C); stainless steel (A213/A249/A269 grades 304L, 316L, 321 — corrosion resistance for most process services, chloride limit 50-500 ppm depending on grade); duplex and super duplex stainless (A789/A790 grades 2205, 2507 — combines high strength with superior chloride and stress corrosion cracking resistance); and specialty alloys including titanium (B338 — seawater and high-chloride service), cupronickel 90/10 and 70/30 (B111 — marine and brackish water with biofouling resistance), and nickel alloys (B622 Hastelloy, B167 Inconel — extreme chemical service and very high temperatures). Tube cost ranges from 1× (carbon steel baseline) to 8-15× (titanium and nickel alloys), but the lifecycle cost depends entirely on whether the material can withstand the service — a $50,000 carbon steel bundle failing every 3 years costs more than a $250,000 titanium bundle lasting 30 years.

A petrochemical plant in Saudi Arabia ordered shell and tube heat exchangers with carbon steel tubes for cooling water service using treated seawater. The capital cost saving was significant — carbon steel tubes cost roughly 20% of titanium equivalents. Within 18 months, the tubes began failing from chloride stress corrosion cracking. Within 36 months, the entire tube bundle required replacement. The replacement cost (in lost production, plant shutdown for retubing, expedited shipping for titanium replacements) was three times the original capital saving. The lesson cost the plant operators approximately $4 million in total.

This is the heat exchanger tube material selection problem in one example. The tube material is one of the smallest line items in a heat exchanger specification but has the largest impact on total cost of ownership. Choose the wrong material and the equipment fails years before its design life. Choose an unnecessarily expensive material and the capital investment is wasted on corrosion resistance the application doesn't need.

The decision involves balancing six factors: corrosion resistance to the specific fluids on both sides of the tube, temperature compatibility through the operating range, mechanical strength at temperature, fabrication economics (carbon steel is easy to weld, titanium requires controlled atmosphere), thermal conductivity (matters for heat transfer area but not as much as commonly believed), and galvanic compatibility with tubesheet and shell materials. The right material satisfies all six.

For mechanical engineers specifying heat exchangers, materials engineers reviewing procurement, project managers evaluating capital cost versus lifecycle cost, and EPC contractors writing specifications — this guide covers all major heat exchanger tube materials, the standards governing them, the service-specific selection criteria, and the galvanic and fabrication considerations that determine long-term performance.

For complete coverage of heat exchanger types, see our Heat Exchangers Pillar Guide. For the specific equipment that uses these tubes, see Shell & Tube Heat Exchangers: TEMA Types, Plate Heat Exchangers, and Air Cooled Heat Exchangers.

Tube Material Standards Overview

Heat exchanger tubes are governed by ASTM, ASME, and equivalent international standards. The major standards by material family:

Welded vs seamless: Welded tubes are generally lower cost and acceptable for most services. Seamless tubes are required for: (1) very high pressure applications, (2) hydrogen service, (3) some refinery process service per project specifications. Most cooling water and utility services use welded tubes economically.

Tube dimensions: Standard tube sizes are typically 12.7mm (1/2"), 19.05mm (3/4"), 25.4mm (1"), and 31.75mm (1-1/4") outside diameter. Wall thickness is specified in BWG (Birmingham Wire Gauge): commonly 14 BWG (2.11mm) for standard service, 12 BWG (2.77mm) for higher pressure, 16 BWG (1.65mm) or 18 BWG (1.24mm) for thinner walls in some non-pressure applications.

Carbon Steel Tubes (The Baseline)

Carbon steel is the default material for heat exchanger tubes in non-corrosive service. It establishes the cost baseline against which all other materials are compared.

Carbon Steel Specifications

ASTM A179 — Seamless cold-drawn low-carbon steel for heat exchanger and condenser tubes. The most common specification for cooling water service.

• Carbon content: 0.06-0.18%

• Tensile strength: ≥325 MPa (47 ksi)

• Yield strength: ≥180 MPa (26 ksi)

ASTM A192 — Seamless carbon steel for high-pressure service.

• Slightly higher strength than A179

• Used in boiler and high-pressure feedwater applications

ASTM A210 — Seamless medium-carbon steel for boiler service. Two grades:

• Grade A-1: lower carbon, more ductile

• Grade C: higher strength, used for some refinery service

ASTM A214 — Welded carbon steel tubes. Economical alternative to seamless for moderate-pressure service.

Applications

Operating Limits

• Temperature: Up to 425°C for short-term peaks; 400°C continuous service practical

• Pressure: Limited primarily by wall thickness; standard tubes handle 100+ bar

• Corrosion limits: Not suitable for acids, chlorides (>50 ppm), aggressive chemicals

• Service life with clean water: 20-30 years

• Service life with chlorides or aggressive fluid: Reduced to 5-10 years (rapid corrosion)

Why Carbon Steel Is Often the Wrong Choice

Despite its low capital cost, carbon steel is the wrong choice for many applications because:

• Chloride content above 50 ppm causes general corrosion within 2-5 years

• Acidic conditions destroy tubes within months

• Pitting corrosion concentrates at small areas

• Galvanic corrosion when paired with stainless tubesheets

• Iron oxide deposits foul heat transfer surfaces

For projects with any chloride concern (cooling tower water with high evaporation, brackish water cooling, seawater), carbon steel is rarely the right answer despite the cost attraction.

Stainless Steel Tubes (The Industrial Standard)

Stainless steel is the standard for most heat exchanger tube applications requiring corrosion resistance. It balances cost against performance better than any other family.

Standard Austenitic Grades

Type 304L (UNS S30403)

• Composition: 18-20% Cr, 8-12% Ni, low carbon (<0.03%)

• Standard: ASTM A213/A249/A269

• Best for: General service, mild process fluids, fresh water service, food/beverage processing

• Chloride limit: Up to 50 ppm at 60°C+ (stress corrosion cracking risk above)

• Cost: ~3.5× carbon steel

Type 316L (UNS S31603)

• Composition: 16-18% Cr, 10-14% Ni, 2-3% Mo, low carbon

• Standard: ASTM A213/A249

• Best for: Standard industrial duties, food/pharmaceutical, marine secondary loops, chemical processing

• Chloride limit: Up to 500 ppm at moderate temperatures (better than 304L due to molybdenum)

• Cost: ~4.5× carbon steel

Type 317L (UNS S31703)

• Composition: Similar to 316L but higher molybdenum (3-4%)

• Better chloride resistance than 316L

• Used in chemical processing with higher chloride content

• Cost: ~5× carbon steel

Type 321 (UNS S32100)

• Composition: 17-19% Cr, 9-12% Ni, with titanium stabilization

• Best for: High-temperature service (>500°C) where intergranular corrosion is concern

• Used in petrochemical and refinery high-temperature service

• Cost: ~4× carbon steel

Operating Limits

For complete coverage of stainless steel grades for process equipment, see Stainless Steel Plate: Grades 304, 316, 321.

Stainless Steel Failure Modes

Even with good general corrosion resistance, stainless steel can fail in specific conditions:

Chloride Stress Corrosion Cracking (SCC): The most common stainless failure. Occurs when chloride concentration, temperature (>60°C), and tensile stress combine. 304L is highly susceptible above 50 ppm; 316L tolerates more but fails above 500 ppm. The cracks are intergranular and difficult to detect until failure.

Pitting and Crevice Corrosion: Localized attack at chloride concentration peaks. Pits can penetrate tube walls in months. Crevice corrosion at tube-to-tubesheet joints is especially problematic.

Intergranular Corrosion (IGC): Carbide precipitation at grain boundaries during welding or sustained high temperature (sensitization range 425-815°C). Use L-grade (low carbon) materials to prevent.

Polythionic Acid Stress Corrosion: Specific to sulfur-containing services during shutdowns when sulfur oxides form acids. Mitigated by neutralization procedures.

Duplex and Super Duplex Stainless Steels

Duplex stainless steels combine austenitic and ferritic microstructures, providing higher strength than standard austenitics and better chloride resistance.

Duplex Grades

Duplex 2205 (UNS S31803/S32205)

• Composition: 22% Cr, 5% Ni, 3% Mo, with 0.14-0.20% N

• Standard: ASTM A789/A790

• Best for: Oil and gas service, offshore, chloride-bearing applications, chemical processing

• Strength: 2× of 316L (allows thinner walls)

• Chloride limit: ~1,500 ppm at 60°C

• Cost: ~6× carbon steel

Super Duplex 2507 (UNS S32750)

• Composition: 25% Cr, 7% Ni, 4% Mo, with 0.24-0.32% N

• Standard: ASTM A789/A790

• Best for: Severe chloride service, offshore platforms, desalination

• Strength: 2.5× of 316L

• Chloride limit: ~10,000 ppm at moderate temperatures

• Cost: ~9× carbon steel

Why Duplex Is Often the Best Choice

For chloride-bearing service that doesn't quite need titanium, duplex offers compelling advantages:

• Higher strength allows thinner wall tubes, reducing weight and cost

• Better SCC resistance than austenitic at equivalent or lower cost

• Lower weight than equivalent shell and tube with austenitic tubes

• 30+ year service life in chloride service that destroys 316L

For offshore platforms in the Gulf of Mexico, Persian Gulf, and North Sea, duplex has largely replaced 316L for cooling water applications. The lifecycle economics justify the capital premium.

Operating Limits

Note: Duplex stainless is limited to ~250°C maximum continuous temperature because of metallurgical changes that can occur with prolonged exposure to higher temperatures (sigma phase precipitation).

Titanium Tubes

Titanium is the premium material for seawater and high-chloride service. The corrosion immunity is so complete that the metal essentially never corrodes in chloride environments.

Titanium Specifications

Grade 2 (UNS R50400) — Commercially pure titanium

• Most common grade for heat exchanger tubes

• Standard: ASTM B338

• Strength: 240-340 MPa

• Temperature limit: 250°C continuous, 320°C peak

Grade 7 (UNS R52400) — Titanium with 0.15% palladium

• Improved corrosion resistance in reducing environments

• Used for hot acids and reducing chemical service

• Standard: ASTM B338

• Significantly more expensive than Grade 2

Grade 12 (UNS R53400) — Titanium with molybdenum/nickel

• Better corrosion in reducing chemicals

• Some welded applications

Why Titanium for Seawater

Titanium is the only practical material for prolonged seawater service:

• Corrosion immunity: Effectively zero corrosion rate in seawater at any temperature, any chloride concentration

• Service life: 30+ years in marine applications (often outlasting the rest of the equipment)

• No fouling-related issues: Smooth surface resists scale buildup

• No galvanic corrosion when used as the cathodic material

Examples of titanium applications:

• Marine engine cooling (seawater to fresh water heat exchangers)

• Coastal refineries with seawater cooling

• Offshore platforms with seawater intake systems

• Desalination plants

• Brackish water cooling (Persian Gulf, Caspian Sea, etc.)

• Highly chlorinated cooling water (cooling tower with high cycles)

Cost vs Lifecycle Economics

Titanium tubes cost 8-12× carbon steel equivalents. For a 1,000-tube bundle, the cost premium might be $500,000-1,000,000 versus carbon steel.

However, in chloride service the lifecycle math is overwhelming:

• Carbon steel: fails in 2-3 years, requires complete replacement

• Stainless 316L: fails in 3-5 years (chloride SCC), bundle replacement

• Duplex 2205: fails in 10-15 years (limit reached)

• Titanium: 30+ years (no replacement needed)

For 30-year facility life: titanium saves 5-10 bundle replacements vs carbon steel.

Copper-Based Alloy Tubes (Marine and Brackish Water)

Copper alloys offer good thermal conductivity and inherent biofouling resistance — making them valuable for specific marine applications.

Cupronickel Specifications

Cupronickel 90/10 (CuNi10Fe1Mn, UNS C70600)

• Composition: 88% Cu, 10% Ni, 1.4% Fe, 1.0% Mn

• Standard: ASTM B111

• Best for: Standard marine cooling, brackish water, surface condensers

• Temperature limit: 150°C

• Chloride limit: Essentially unlimited (seawater)

Cupronickel 70/30 (CuNi30Fe1Mn, UNS C71500)

• Composition: 68% Cu, 30% Ni, 0.7% Fe, 0.7% Mn

• Standard: ASTM B111

• Best for: Severe marine service, high-velocity applications, polluted seawater

• Better than 90/10 in higher-velocity service (>3 m/s)

• Higher cost than 90/10

Admiralty Brass (CuZn28Sn1, UNS C44300)

• Composition: 70% Cu, 28% Zn, 1% Sn (tin-inhibited)

• Lower cost than cupronickels

• Used in some condensers (largely replaced by cupronickels in modern applications)

• Susceptible to dezincification in some waters

Why Cupronickel for Marine

Cupronickels have three properties that make them ideal for marine cooling:

1. Biofouling resistance: Copper-based alloys release small amounts of copper ions that prevent biological growth on the tube surface. This is why coast guard ships, navy vessels, and merchant marine use cupronickel for sea chests and seawater systems.

2. Good thermal conductivity: Thermal conductivity is ~50-60 W/m·K — better than stainless steel (~15 W/m·K) but lower than copper (~400 W/m·K). This improves heat transfer compared to stainless.

3. Moderate cost: Cupronickel 90/10 costs about 3-4× carbon steel and 30-40% less than titanium for marine service.

Limitations

• Maximum velocity limited (typically <3 m/s for 90/10, <4 m/s for 70/30)

• Higher cost than stainless for non-marine applications

• Galvanic compatibility issues with steel tubesheets

• Erosion-corrosion in high-velocity service (above 5 m/s)

• Sulfide pollution can cause rapid attack

• Ammonia sensitivity (causes stress corrosion cracking)

Marine Tube Selection Decision

Nickel Alloys (Extreme Service)

Nickel-based alloys handle the most demanding chemical service and highest temperatures. They are premium materials with premium costs.

Standard Nickel Alloys

Inconel 600 (UNS N06600)

• Composition: 72% Ni, 15-17% Cr, 6-10% Fe

• Standard: ASTM B167

• Temperature limit: 815°C continuous

• Best for: High-temperature aqueous service, nuclear primary loops, oxidizing environments

Inconel 625 (UNS N06625)

• Composition: 58% Ni, 20-23% Cr, 8-10% Mo

• Standard: ASTM B704

• Temperature limit: 980°C peak

• Best for: Seawater, severe acid service, high-temperature gas service

• The most versatile nickel alloy

Incoloy 800 (UNS N08800)

• Composition: 30-35% Ni, 19-23% Cr, balance Fe

• Standard: ASTM B163

• Temperature limit: 815°C continuous

• Used in petrochemical high-temperature service

Incoloy 825 (UNS N08825)

• Composition: 38-46% Ni, 19-23% Cr, 2.5-3.5% Mo

• Standard: ASTM B163

• Excellent in sulfuric acid, phosphoric acid service

• Better than 316L in chloride at lower cost than Hastelloy

Hastelloy C276 (UNS N10276)

• Composition: 57% Ni, 14-16% Cr, 15-17% Mo, 3-5% W

• Standard: ASTM B622

• Best for: Most aggressive chemical service, organic acids, oxidizing-reducing mixed acids

• Premium cost (~15× carbon steel)

Hastelloy C22 (UNS N06022)

• Higher Cr content than C276 (~22%)

• Better for oxidizing acids

• Standard: ASTM B622

• Used in waste handling, severe chemical processing

Selection Guide for Nickel Alloys

Cost Considerations

Nickel alloys cost 8-15× carbon steel. They are specified when:

• Stainless and duplex are inadequate for the service

• Failure cost exceeds capital cost premium

• Service life of 25+ years is required

• Maintenance access is limited (offshore, remote)

Galvanic Corrosion Considerations

When two different metals are connected (tube to tubesheet, tube to shell), galvanic corrosion can attack the more anodic (more reactive) material. This is critical in tube selection.

Galvanic Series (Most Anodic to Most Cathodic)

In seawater service:

1. Most anodic (most reactive — corrodes first):

   • Magnesium, zinc

   • Aluminum

   • Carbon steel (very anodic in seawater)

2. Mid-range:

   • Low alloy steels

   • 304L stainless (in seawater, can be active)

   • Brass and bronze alloys

3. More cathodic:

   • Cupronickel 90/10

   • Cupronickel 70/30

   • 316L stainless

4. Most cathodic (most noble — least likely to corrode):

   • Duplex stainless

   • Nickel alloys

   • Titanium (most noble)

Common Galvanic Problems

Carbon steel tubesheet + stainless tubes: Stainless is more noble (cathodic); carbon steel tubesheet corrodes preferentially near the tube joints. Requires cathodic protection or clad tubesheet.

Stainless tubesheet + titanium tubes: Titanium is much more noble; stainless tubesheet corrodes severely. Often requires titanium clad tubesheet, sacrificial anodes, or impressed current protection.

Cupronickel tubes + stainless tubesheet: Cupronickel is more anodic; cupronickel tubes corrode. Use cupronickel tubesheet or clad with same material.

Aluminum bronze tubesheet + stainless or titanium tubes: Aluminum bronze is anodic; tubesheet attack is severe. Use cathodic protection or change tubesheet material.

Mitigation Methods

1. Clad tubesheets: Tubesheet has a thin layer of the same material as tubes welded to its surface. The exposed surface (tubes side) is the cladding material. Used for titanium tubes with carbon steel structural tubesheet.

2. Same material throughout: Match all wetted parts to the tube material. Eliminates galvanic difference but increases cost.

3. Sacrificial anodes: Zinc or magnesium anodes installed in waterboxes provide cathodic protection. The anode corrodes preferentially, protecting tubes and tubesheet.

4. Impressed current cathodic protection (ICCP): Powered system applying small DC current to make the equipment more cathodic. Used in large marine installations.

5. Coatings: Specific epoxy or vinyl ester coatings on tubesheets reduce direct exposure.

Heat Exchanger Service Selection Matrix

Putting it all together — recommended materials by typical service:

Common Material Selection Mistakes

After 15+ years supplying heat exchanger equipment to industrial and process customers:

Mistake 1: Specifying Carbon Steel for Brackish Water

Buyer specifies carbon steel A179 for "treated cooling water" without confirming chloride content. Source water has 800 ppm chlorides; tubes corrode within 2 years; complete bundle replacement.

Prevention: Always confirm actual chloride concentration of cooling water — at source AND after concentration in the cooling tower (cycles of concentration typically 4-6×). For any chloride >50 ppm, specify minimum 316L; for chloride >500 ppm, specify duplex or cupronickel.

Mistake 2: 304L in Chloride Service

Buyer specifies 304L for cost reasons in cooling tower water with 100 ppm chlorides. Within 18 months, chloride SCC produces tube failures.

Prevention: 304L is limited to ≤50 ppm chlorides at temperatures above 60°C. For higher chloride OR higher temperature, specify 316L minimum. Never use 304L for cooling tower service in arid climates where cycles concentrate chlorides.

Mistake 3: Wrong Cupronickel Grade

Buyer specifies 90/10 cupronickel for severe service where 70/30 is needed (high velocity, polluted seawater). Erosion-corrosion attacks tubes within 5-8 years.

Prevention: Cupronickel 90/10 limit is approximately 3 m/s velocity. For higher velocities or polluted seawater, specify 70/30. For extreme service, consider titanium.

Mistake 4: Wrong Tubesheet Material

Buyer specifies titanium tubes with stainless tubesheet to save cost. Galvanic corrosion attacks the tubesheet at every tube joint within 2-3 years; tube-to-tubesheet seals fail; bundle requires complete rebuild.

Prevention: For titanium tubes, specify titanium clad tubesheet or sacrificial anode cathodic protection. Galvanic compatibility is mandatory.

Mistake 5: Ignoring Operating Temperature

Buyer specifies 304L tubes for refinery service at 550°C. Sustained high temperature causes carbide precipitation (sensitization), making the steel susceptible to intergranular corrosion during shutdowns.

Prevention: For service above 425°C, use stabilized stainless (321) or low-carbon (304L, 316L). For service above 540°C, consider Incoloy 800 or 321/347.

Mistake 6: Wrong Specification for Sour Service

Buyer specifies standard carbon steel for refinery service containing sulfur compounds. Sulfide stress corrosion cracking (SSCC) causes catastrophic failure during shutdown.

Prevention: For sour service, specify NACE MR0175/MR0103-compliant materials. Carbon steel must have controlled hardness; alloy options include sour service-rated stainless and nickel alloys.

Mistake 7: Inadequate Wall Thickness

Buyer specifies 18 BWG (1.24mm) tubes to minimize material cost. For seawater service with potential pitting, the thin wall doesn't provide enough corrosion allowance; pinhole leaks appear after 3-5 years.

Prevention: For corrosion-allowance applications (chlorides, acids), use minimum 14 BWG (2.11mm). Thinner walls are appropriate only for clean service with no corrosion concerns.

Tube Specification Template

PROJECT: [Project Name]
APPLICATION: [Service description]
LOCATION: [Country, Facility]

PROCESS SIDE:
- Fluid: [Composition with key contaminants]
- Operating temperature: [°C]
- Operating pressure: [bar]
- Velocity: [m/s typical]
- Maximum corrosion concentration: [Specific chemicals/concentrations]
- Sulfide concentration (if H₂S service)
- Chloride concentration (if applicable)
- pH range

SHELL SIDE:
- Fluid: [Composition]
- Operating temperature: [°C]
- Operating pressure: [bar]
- Velocity: [m/s]
- Corrosion concerns: [Specific]

DESIGN CONDITIONS:
- Design temperature: [°C]
- Design pressure: [bar]
- Code compliance: [ASME Section VIII Div 1, etc.]

TUBE SPECIFICATION:
- Material: [Specific grade, e.g., ASTM A213 TP316L]
- Standard: [ASTM A179, A213, A249, B111, B338, B622]
- Welded/seamless: [As required]
- Outside diameter: [mm — typically 19, 25, 32]
- Wall thickness: [BWG — typically 14 BWG = 2.11mm]
- Length: [m]
- Temper/condition: [As needed]

TUBESHEET COMPATIBILITY:
- Tubesheet material: [Specified]
- Galvanic compatibility verified: [Yes/No]
- Clad tubesheet required: [Yes/No]
- Cathodic protection: [Required/Not required]

QUALITY REQUIREMENTS:
- Hydrostatic test pressure: [bar]
- Non-destructive examination: [Eddy current, ultrasonic, hydrostatic]
- Visual inspection requirements
- Surface finish: [Standard or polished]
- Heat treatment: [Solution annealed for stainless]

DOCUMENTATION REQUIRED:
- Mill test certificates (EN 10204 Type 3.1)
- Heat number traceability
- Chemical composition certificate
- Mechanical test certificate
- Hydrostatic test certificate
- NDE inspection reports
- Welding procedure qualifications (for welded tubes)

DELIVERY:
- Required date: [Date]
- Shipping terms: [FOB / CIF / DDP]
- Delivery location: [Full address]
- Packaging: [Standard wood crating or specialty]

Supply from Kasko Makine

Kasko Makine supplies heat exchanger tubes in all major material families for shell and tube heat exchangers, condensers, coolers, and process exchangers across refining, petrochemical, power generation, marine, food/pharma, and process industries:

Carbon steel tubes:

• ASTM A179 seamless (cooling water, condensers)

• ASTM A192 high-pressure seamless

• ASTM A210 boiler service

• ASTM A214 welded (economical alternative)

Stainless steel tubes:

• ASTM A213 seamless: 304L, 316L, 317L, 321, 347

• ASTM A249 welded: 304L, 316L, 321

• ASTM A269 specialty grades

• All in various dimensions and wall thicknesses

Duplex and Super Duplex:

• ASTM A789/A790: Duplex 2205, Super Duplex 2507

• Both welded and seamless

• For chloride service, offshore, severe industrial duty

Titanium tubes:

• ASTM B338 Gr 2 (commercially pure)

• ASTM B338 Gr 7 (palladium-stabilized)

• Standard and custom diameters

Copper alloys:

• ASTM B111 Cupronickel 90/10 and 70/30

• ASTM B543 Admiralty brass (limited availability)

• For marine, seawater, brackish water applications

Nickel alloys:

• ASTM B167 Inconel 600

• ASTM B704 Inconel 625

• ASTM B163 Incoloy 800 and 825

• ASTM B622 Hastelloy C276 and C22

• For extreme chemical service

Tube dimensions:

• Outside diameter: 12.7mm to 50.8mm standard

• Wall thickness: 1.24mm (18 BWG) to 3.40mm (10 BWG)

• Lengths: 1m to 12m (custom up to 15m)

• U-bent tubes available with controlled radius

Documentation per shipment:

• Mill test certificates (EN 10204 Type 3.1)

• Heat number traceability with complete records

• Chemical and mechanical test certificates

• Hydrostatic test certificates

• Eddy current testing reports (for stainless and nickel alloys)

• Ultrasonic testing reports (where specified)

• NACE compliance (for sour service)

• ASME Section II material certifications

• PED compliance for European projects

Engineering services:

• Materials selection consultation for specific service conditions

• Corrosion analysis review

• Galvanic compatibility verification

• Lifecycle cost analysis comparing material options

• Tubesheet material recommendations

• Cathodic protection specification

Need heat exchanger tubes? Send us your service description (process and shell side fluids, temperatures, pressures, contaminants, especially chlorides and sulfur), required material grade, tube dimensions, quantity, and delivery location to info@kaskomakine.com or WhatsApp +90 (537) 521 1399. Our materials engineering team will verify your specification, recommend optimizations where applicable, and provide complete pricing with delivery schedule within 48 hours.

Continue Reading: Heat Exchanger Series

This tube materials guide is part of our comprehensive heat exchanger series:

• Heat Exchangers: Complete Guide — The master pillar covering all heat exchanger types

• Shell & Tube Heat Exchangers: TEMA Types — Configuration deep-dive (these tubes go in TEMA-spec exchangers)

• Plate Heat Exchangers: Types & Selection — Plate alternative (different materials apply to plates)

• Air Cooled Heat Exchangers — Air-cooled service (same tube materials with extended-surface fins)

• Shell & Tube vs Plate Heat Exchanger — Comparison framework

• Stainless Steel Plate: Grades 304, 316, 321 — Materials context for stainless tubes

• Carbon Steel Plate: ASTM A516 & A36 — Carbon steel materials context

FAQ SCHEMA

Q: What are the most common heat exchanger tube materials?
A: The most common heat exchanger tube materials are: carbon steel (ASTM A179 for cooling water, A192 for high pressure, A210 for boiler service) — the lowest cost baseline; stainless steel (ASTM A213 grades 304L, 316L, 317L, 321) — the standard for corrosion resistance; duplex stainless (ASTM A789 grade 2205, super duplex 2507) — for chloride service; titanium (ASTM B338 Grade 2) — for seawater and high-chloride service; cupronickel (ASTM B111 grades 90/10 and 70/30) — for marine and brackish water; and nickel alloys (Inconel, Incoloy, Hastelloy) — for extreme chemical service. Cost ranges from 1× baseline (carbon steel) to 15× (Hastelloy C276).

Q: When should I use stainless steel tubes vs carbon steel?
A: Specify stainless steel over carbon steel when: (1) cooling water chloride concentration exceeds 50 ppm (carbon steel corrodes), (2) operating temperature exceeds 425°C (carbon steel oxidation), (3) acidic conditions exist (any pH below 6), (4) operating pressure is very high requiring corrosion margin, (5) service life of 20+ years is expected, (6) downtime cost is high. For clean fresh water cooling, clean hydrocarbon service, and standard steam condensing — carbon steel A179 remains the most economical choice with adequate service life.

Q: What is duplex stainless steel and when is it used?
A: Duplex stainless steels (such as 2205, UNS S31803/S32205) have a dual-phase microstructure of austenite and ferrite, giving them approximately twice the strength of standard austenitic stainless (316L) along with superior chloride resistance. They handle chloride concentrations up to 1,500 ppm (versus 500 ppm for 316L). Super duplex 2507 handles up to 10,000 ppm chloride. Duplex is the standard material for offshore platforms, oil and gas service, desalination plants, and chemical processing with chloride-bearing fluids. The higher strength allows thinner tube walls, reducing weight and partially offsetting the cost premium (typically 6-9× carbon steel).

Q: Why are cupronickel tubes used for marine applications?
A: Cupronickel alloys (90/10 and 70/30) are preferred for marine cooling because they combine three critical properties: (1) biofouling resistance — copper ions released from the tube surface inhibit biological growth, eliminating biofouling that destroys other materials in seawater, (2) good thermal conductivity (~50-60 W/m·K, better than stainless), and (3) moderate cost (3-4× carbon steel, 30-40% less than titanium). Cupronickel 90/10 is standard for general marine service up to 3 m/s velocity; 70/30 handles higher velocity and polluted seawater. For severe service or very high velocity, titanium replaces cupronickel.

Q: When do I need titanium tubes in a heat exchanger?
A: Titanium tubes are essential when: (1) cooling water is seawater or has very high chloride content (above 1,500-3,000 ppm), (2) chloride stress corrosion cracking has destroyed previous bundles of stainless, (3) very long service life (30+ years) is required, (4) downtime cost exceeds capital cost premium by 5-10×. Titanium provides essentially zero corrosion rate in chloride service at any concentration and temperature. The capital cost premium is significant (8-12× carbon steel) but the lifecycle economics favor titanium in marine and desalination applications where alternatives fail within 3-15 years.

Q: What is galvanic corrosion and how is it prevented in heat exchangers?
A: Galvanic corrosion occurs when two different metals are in electrical contact with an electrolyte (like seawater). The more anodic (reactive) metal corrodes preferentially. For heat exchangers, the typical concern is tube-to-tubesheet connections where dissimilar metals meet. Common problems include: carbon steel tubesheet with stainless tubes (carbon steel corrodes), stainless tubesheet with titanium tubes (stainless corrodes severely). Prevention methods: (1) clad tubesheets matching tube material, (2) same material throughout (most reliable), (3) sacrificial anodes (zinc, magnesium) in waterboxes, (4) impressed current cathodic protection, (5) careful design separation of dissimilar metals.

Q: How do I select the right wall thickness for heat exchanger tubes?
A: Tube wall thickness is selected based on operating pressure and corrosion allowance. Standard wall thicknesses in BWG (Birmingham Wire Gauge): 18 BWG (1.24mm) — used for clean low-pressure service without corrosion concerns; 16 BWG (1.65mm) — moderate service; 14 BWG (2.11mm) — standard for most industrial heat exchangers including corrosion-resistant alloys; 12 BWG (2.77mm) — high-pressure service or significant corrosion allowance. For materials prone to pitting or stress corrosion (stainless in chloride, cupronickel in polluted seawater), use minimum 14 BWG to provide corrosion allowance. Thinner walls (18 BWG) are appropriate only for clean service with established corrosion data.