ASTM B111 C68700 Aluminium Brass Tubes – Complete Technical Guide

GNEE stands as a prominent manufacturer and supplier of top-quality aluminium brass seamless tubes conforming to ASTM B111 / ASME SB111. Committed to excellence, we ensure our C68700 alloy tubing meets the highest corrosion resistance, thermal conductivity, and mechanical strength standards. Our state-of-the-art manufacturing processes and stringent quality control measures guarantee reliability and consistency in every aluminum brass condenser tube produced.

Choose GNEE for superior UNS C68700 heat exchanger tubing that meets your exact specifications and exceeds your expectations.

We successfully supplied ASTM B111 C68700 aluminum brass tubes to a customer in India for shell & tube condenser applications. During the project, the customer visited our facility for production inspection and quality verification. All tubes were manufactured in accordance with ASTM B111 requirements and delivered with complete Material Test Certificates (MTC), ensuring full heat number traceability and verified chemical and mechanical properties.

Aluminium brass alloy C68700 (EN CW702R / BS CZ110) is a specific copper-zinc-aluminium mixture with high corrosion resistance and excellent thermal conductivity. These dezincification resistant tubes are commonly used in numerous industries, including:

Petrochemical industry

Power generation plants

Marine applications

Desalination plants

HVAC systems

Refineries

The most outstanding feature of 2.0460 aluminium brass tubes is their great strength in resisting corrosion in seawater and other harsh environmental conditions. This makes them ideal for marine applications such as surface condensers, shell and tube heat exchangers, and saltwater piping systems.

Apart from being resistant to corrosion, CW702R seamless tubing also exhibits good thermal conductivity, making them suitable for heat transfer applications where efficient thermal exchange is required.

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The manufacturing of 2.0460 aluminium brass tubes involves the following steps:

GNEE offers various types of aluminium brass tubes conforming to ASTM B111 / EN CW702R:

BS CZ110 / UNS C68700 / EN CW702R tubes are widely used in the following industries:

High resistance to impingement attack – ideal for high-velocity seawater above 2.5 m/s

Excellent corrosion resistance in marine, saltwater, and brackish water environments

Good thermal conductivity (100.4 W/m·K) for efficient heat exchange

Lightweight compared to many other copper alloys

High low-temperature strength for cryogenic applications

Resists dezincification due to aluminium and arsenic addition

Easy to fabricate – can be soldered, brazed, or welded

Long service life in severe environments, reducing maintenance needs

1. What is the difference between UNS C68700 (Aluminium Brass) and UNS C70600 (Copper-Nickel) for power plant condenser tubes?

UNS C68700 is an aluminium brass alloy containing 76-79% copper and 1.8-2.5% aluminium, offering excellent resistance to high-velocity seawater impingement. UNS C70600 is a 90/10 copper-nickel alloy with 88% copper and 10% nickel, preferred for superior resistance to general seawater corrosion and biofouling. For condenser tubes in power plants with cooling water velocities above 2.5 m/s, choose C68700 aluminium brass. For marine piping systems where biofouling is a concern, choose C70600 copper-nickel.

2. What are the EN and DIN equivalent grades for UNS C68700 aluminium brass seamless tubes?

The European equivalent for UNS C68700 is EN CW702R (CuZn20Al2As) . The German (DIN) equivalent is 2.0460. The British standard equivalent is BS CZ 110. These aluminium brass grades are fully interchangeable for heat exchanger tubes and condenser tubes in seawater applications across international standards. All have the same 1.8-2.5% aluminium content and 0.02-0.06% arsenic addition for dezincification resistance.

3. What is the standard outer diameter range for ASTM B111 C68700 seamless heat exchanger tubes?

ASTM B111 C68700 seamless tubes are available in an outer diameter range of 4mm to 150mm. For heat exchanger applications, common diameters include 12.7mm (1/2 inch), 15.9mm (5/8 inch), 19.05mm (3/4 inch), and 25.4mm (1 inch) . Wall thickness ranges from 0.25mm to 8mm depending on the application pressure and temperature requirements.

4. Can EN CW702R aluminium brass tubes be welded for custom desalination plant evaporators?

Yes, EN CW702R (CuZn20Al2) aluminium brass tubes can be welded, soldered, or brazed for custom desalination plant evaporators and distillers. However, proper annealing above 650°C is recommended after severe welding or forming to restore corrosion resistance. For high-pressure applications in thermal desalination, seamless C68700 tubes are preferred over welded tubes to avoid weld seam corrosion.

5. What is the maximum operating temperature for BS CZ110 aluminium brass condenser tubes in power stations?

BS CZ110 aluminium brass condenser tubes have an ideal working temperature range of 760°C to 871°C for short-term exposure. However, for continuous service in power station condensers and heat exchangers, operating temperatures should be kept below 200°C to maintain mechanical integrity and optimal corrosion resistance in seawater cooling systems.

6. What is the purpose of arsenic (As) in DIN 2.0460 aluminium brass distiller tubes?

DIN 2.0460 (CuZn20Al2As) distiller tubes contain 0.02-0.06% arsenic (As) . Arsenic is added to inhibit dezincification – a selective leaching of zinc from the aluminium brass alloy. This makes 2.0460 tubes highly suitable for distiller tubes, evaporator tubes, and condenser tubes in seawater and brackish water applications where dezincification could otherwise cause premature tube failure within months.

7. What quality tests are performed on ASTM B111 C68700 heat exchanger tubes before shipment by GNEE?

GNEE performs the following quality tests on ASTM B111 C68700 heat exchanger tubes: expansion test (to determine expansion limit), flattening test (to analyze flattening resistance), hydrostatic test (leak detection at 1000-3000 psi), nondestructive eddy current test (for surface defects), residual stress test (for durability under working stress), and grain size test (0.010-0.045mm requirement). Third-party inspections (BV, SGS, TUV, Lloyds) are available upon request at additional cost.

8. What is the minimum order quantity (MOQ) for UNS C68700 aluminium brass seamless tubes from GNEE?

For UNS C68700 aluminium brass seamless tubes in standard heat exchanger sizes (e.g., 19.05mm OD x 1.65mm wall thickness), the MOQ can be as low as 500 kg (approximately 200-300 meters) . For custom diameters, wall thicknesses, or lengths outside standard ASTM B111 ranges, higher MOQs of 1000-2000 kg may apply. Contact GNEE directly with your specifications for a firm MOQ quotation.

9. What is the thermal conductivity of CuZn20Al2 alloy, and why does it matter for shell and tube heat exchangers?

The thermal conductivity of CuZn20Al2 (CW702R / C68700) is 58.0 BTU·in/hr·ft²·°F at 68°F (100.4 W/m·K at 20°C) . This is approximately 20% lower than pure copper but still excellent for most industrial heat transfer applications. This thermal conductivity makes C68700 tubes highly efficient for shell and tube heat exchangers, condensers, and evaporators, as it allows rapid heat transfer between fluids while maintaining seawater corrosion resistance – a combination that pure copper cannot offer.

10. What is the difference between ASTM B111 C68700 (Aluminium Brass) and ASTM B111 C44300 (Admiralty Brass) for seawater condenser tubes in power plants?

ASTM B111 C68700 (Aluminium Brass) contains 1.8-2.5% aluminium and offers superior resistance to impingement attack in high-velocity seawater (above 2.5 m/s). ASTM B111 C44300 (Admiralty Brass) contains 71% copper, 28% zinc, and 1% tin with 0.02-0.06% arsenic, and is suitable for clean seawater or brackish water with velocities below 2.0 m/s. For power plant condensers with cooling water velocities above 2.5 m/s or with sand/silt particles, C68700 aluminium brass is the recommended choice. For lower velocities (below 2.0 m/s) in cleaner seawater, C44300 Admiralty brass may be adequate and more cost-effective.

Every tube in this lot has passed third-party witnessed inspection per ASTM B111 standard for C68700 alloy. Below are actual photos from customer-onsite inspection, including eddy current testing and dimensional verification.

Inspection items verified:
• Eddy current testing (ECT) – no through-wall defects
• Outer diameter & wall thickness – within ±0.02mm tolerance
• Surface finish & temper (O61) – conforms to ASTM
• Hardness & chemical composition – certified.

After passing inspection, all tubes are packed according to export standards and customer-specific requirements. The packing process is documented below to ensure traceability and damage-free delivery.

Packing steps shown in video & images:
1. Tube cleaning & drying
2. Plastic end caps on both ends
3. VCI anti-rust paper wrapping
4. Bundle strapping with moisture barrier film
5. Plywood wooden case (ISPM-15 compliant) with foam padding
6. Labeling with ASTM grade, lot number, and inspection stamp

All ASTM C68700 tubes are produced and inspected on our in-house equipment, allowing full process control from billet casting to final packing.

Key equipment used for this lot:
• Induction melting furnace – precise alloying (Cu + Zn + Al + As)
• Horizontal continuous casting – uniform billet structure
• Extrusion press (800T / 1630T) – seamless tube forming
• Cold drawing bench (5–40m) – dimensional accuracy to ±0.02mm
• Online eddy current tester (FOERSTER / MAC) – 100% NDT
• Ultrasonic wall thickness gauge – real-time monitoring
• Annealing furnace (controlled atmosphere) – temper O61

In-house metrology: Micrometers, pin gauges, optical comparator, hardness tester (HV/HRB)

All equipment is calibrated quarterly. Production records are traceable by lot number.

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