Why material selection matters for heat exchanger tubes
Pick the wrong tube material, and the heat exchanger leaks within two years. Pick the right one, and it runs for 20 years with minimal maintenance.
ASTM B338 GR1 titanium tube competes directly with copper-nickel alloys (90/10, 70/30) and stainless steel (316L) for shell and tube heat exchanger service. Each has strengths. Each has limits.
For full technical specifications of ASTM B338 GR1 titanium tube, including size ranges and mechanical properties, see the product page here.
Corrosion resistance comparison
| Material | Seawater pitting | Crevice corrosion | Sulfide attack | Ammonia attack |
|---|---|---|---|---|
| GR1 titanium | None | To 80°C | None | None |
| 70/30 Cu-Ni | Moderate | Moderate | Severe | Moderate |
| 90/10 Cu-Ni | Moderate | Moderate | Severe | Moderate |
| 316L stainless | Severe | Severe | None | None (but pitting) |
GR1 titanium has no pitting in seawater. 316L pits within months to years depending on temperature and chlorides. Copper-nickel does not pit but suffers from erosion and sulfide attack.
For polluted or stagnant seawater, copper-nickel fails rapidly due to sulfides. GR1 handles sulfides without issue.
Mechanical properties comparison
| Property | GR1 titanium | 70/30 Cu-Ni | 316L stainless |
|---|---|---|---|
| Tensile strength (min) | 240 MPa | 350 MPa | 485 MPa |
| Yield strength (min) | 138 MPa | 125 MPa | 170 MPa |
| Elongation (min) | 24% | 30% | 35% |
| Density | 4.51 g/cm³ | 8.94 g/cm³ | 8.00 g/cm³ |
| Thermal conductivity | 17 W/m·K | 29 W/m·K | 15 W/m·K |
Titanium is 40–50% lighter than copper-nickel or stainless steel. For the same tube size, a titanium bundle weighs much less. This matters for offshore platforms and mobile equipment.
Thermal conductivity of titanium is lower than copper-nickel. To achieve the same heat transfer, titanium tubes may need thinner walls or more surface area. In practice, the difference is small because titanium tubes can run at higher velocities without erosion.
Velocity limits and erosion resistance
Flow velocity affects both heat transfer and tube life.
| Material | Maximum recommended velocity (seawater) | Erosion mechanism |
|---|---|---|
| GR1 titanium | 5–7 m/s | None (very resistant) |
| 70/30 Cu-Ni | 3–4 m/s | Protective film erodes |
| 90/10 Cu-Ni | 2–3 m/s | Protective film erodes |
| 316L stainless | 3–5 m/s | No erosion, but pitting |
GR1 titanium can run at higher velocities than copper-nickel. Higher velocity improves heat transfer and reduces fouling. This is a significant advantage in condensers and high-flow coolers.
Copper-nickel tubes erode at sand or debris impact points. Titanium does not.
Biofouling comparison
Marine growth attaches to all materials. The difference is cleaning.
| Material | Biofouling attachment | Cleaning tolerance |
|---|---|---|
| GR1 titanium | Moderate | High (water jet to 10,000 psi) |
| 70/30 Cu-Ni | Moderate (copper inhibits) | Low (erodes under jet) |
| 316L stainless | High | Moderate |
Copper-nickel has natural biofouling resistance because copper ions kill marine organisms. This is a real advantage. However, the effect diminishes over time as the surface films develop.
Titanium does not have this property. Biofouling attaches readily. But titanium tolerates aggressive cleaning that would destroy copper-nickel tubes. High-pressure water jetting (5,000–10,000 psi) removes fouling without damaging titanium.
Cost comparison
First cost vs life cycle cost.
| Material | Relative material cost | Typical tube life | Life cycle cost |
|---|---|---|---|
| GR1 titanium (welded) | 3–4x 316L | 20+ years | Lowest for seawater |
| 70/30 Cu-Ni | 2–3x 316L | 10–15 years | Medium |
| 90/10 Cu-Ni | 1.5–2x 316L | 5–10 years | Medium-high |
| 316L stainless | 1x (baseline) | 1–3 years | Highest (frequent replacement) |
316L has the lowest first cost but the highest life cycle cost in seawater service. Frequent retubing means downtime, labor, and lost production.
GR1 has the highest first cost but the lowest life cycle cost for long-term seawater applications. The tube bundle outlasts the rest of the heat exchanger.
Fabrication comparison
| Material | Rolling | Welding | Bending |
|---|---|---|---|
| GR1 titanium | Good (needs clean tools) | Requires argon shielding | Excellent |
| 70/30 Cu-Ni | Excellent | Standard procedure | Good |
| 316L stainless | Good | Standard procedure | Good |
GR1 requires clean tooling and argon shielding for welding. This is not difficult, but it is different from copper-nickel or stainless steel.
Copper-nickel is the easiest to fabricate. It behaves like standard copper alloys. No special shielding or tooling required.
316L is also straightforward but requires attention to heat input to avoid sensitization.
Galvanic corrosion when mixing materials
Different metals in contact with seawater create a battery. One metal corrodes.
| Metal pair in seawater | Result |
|---|---|
| Titanium + copper-nickel | Copper-nickel corrodes (titanium is cathodic) |
| Titanium + 316L | 316L corrodes (titanium is cathodic) |
| Titanium + carbon steel | Carbon steel corrodes rapidly |
| Copper-nickel + 316L | Both corrode, unpredictable |
Titanium is the most cathodic common metal in seawater. When connected to almost any other metal, the other metal corrodes faster.
Isolate titanium tube sheets from dissimilar metals. Use plastic gaskets, coated tube sheets, or titanium-faced tube sheets.
Application recommendations
Specify GR1 titanium when:
Seawater or brackish water on the tube side
Service life required is 15+ years
Polluted or stagnant seawater (sulfides present)
High flow velocity (over 3 m/s)
Weight is a concern (offshore, mobile)
Retubing cost is high (remote location)
Specify copper-nickel when:
Clean seawater only (no sulfides)
Biofouling control is critical and cleaning is difficult
Lower first cost is required
Fabrication with standard shop equipment is necessary
Specify 316L when:
No chlorides in the fluid
Fresh water or clean hydrocarbon service
Low first cost is the only criterion
Discuss Your Project Requirements
FAQ
1. Is titanium always better than copper-nickel for seawater?
For long service life, yes. For short-term or clean seawater applications, copper-nickel works and costs less. GR1 titanium tubing corrosion resistance seawater is superior, but the higher first cost may not be justified for every project.
2. Does copper-nickel really fail in polluted seawater?
Yes. Sulfides from decaying organic matter or industrial discharge destroy the protective film on copper-nickel. Tubes can fail in months. GR1 handles sulfides with no problem.
3. Can 316L ever be used in seawater?
Only in very clean, cold, low-chloride seawater with no stagnation. Even then, expect pitting within 2–3 years. For reliable seawater service, 316L is not recommended.
4. How much more does GR1 cost than 316L?
Typically 3–4 times the material cost. But a 316L bundle may need replacement every 2 years. A GR1 bundle lasts 20+ years. Over 20 years, GR1 is cheaper.
5. Does the lower thermal conductivity of titanium matter?
In most heat exchangers, not much. Titanium tubes can run at higher velocities without erosion, which compensates for the lower conductivity. Many condensers use titanium with the same surface area as copper-nickel.
6. Can GR1 and copper-nickel be mixed in the same heat exchanger?
Not recommended. Galvanic corrosion will attack the copper-nickel. If mixing is unavoidable, isolate electrically and keep the titanium cathode area small.
7. Which copper-nickel grade is better for seawater?
70/30 Cu-Ni lasts longer than 90/10. 90/10 has better biofouling resistance initially but corrodes faster. For long-term seawater, 70/30 is preferred.
8. Does titanium require a corrosion allowance?
No. GR1 does not corrode at a measurable rate in seawater. Tube wall thickness is determined by pressure and handling strength, not corrosion allowance.
9. Which material is easiest to roll into tube sheets?
Copper-nickel is the easiest. GR1 is also good but requires clean, iron-free tooling. 316L is similar to GR1.
10. What is the most common replacement scenario?
316L tubes in seawater coolers failing after 1–3 years, replaced with welded titanium tube ASTM B338 Grade 1. The second most common is copper-nickel in sulfide-bearing water replaced with GR1.
Products Description
We produce GR1 titanium, 90/10 copper-nickel, 70/30 copper-nickel, and 316L stainless steel tubes for heat exchanger service.
Our factory has four dedicated production lines. Titanium tubes run on cold pilger mills and draw benches with argon-filled annealing furnaces.
Copper-nickel tubes use separate draw benches with controlled atmosphere annealing to prevent oxidation. Stainless steel tubes have their own line with different tooling and lubricants.
No cross-contamination between materials. Titanium tooling never touches stainless steel or copper-nickel. Iron pickup from stainless steel would ruin titanium corrosion resistance. Separate tooling prevents this.
Inspection equipment covers all three materials: spectrometer for chemistry verification, ultrasonic flaw detectors, hydrostatic testers, and laser micrometers. Each material type has its own calibration standards.
All tubes come with mill certificates per EN 10204 Type 3.1. Third-party inspection (SGS, BV, TÜV) available for any material.
