C68700 Aluminum Brass (UNS C68700 / CuZn22Al2) – ASTM B111

C68700 aluminum brass is a copper-zinc alloy enhanced with aluminum and arsenic (As) as a corrosion inhibitor. It delivers exceptional resistance to high-velocity seawater and brackish water. Known for its strength and durability, ASTM B111 C68700 is engineered to withstand impingement attack and erosion-corrosion in aggressive cooling environments.

Inhibited aluminum brass tubes (UNS C68700) are widely used in condenser systems, especially in marine, power generation, and desalination settings, where water velocity and salt content challenge the long-term performance of standard copper alloys.

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Exceptional resistance to impingement and erosion: Handles high-velocity water without thinning or surface degradation.

Superior corrosion resistance in salt and brackish water: Aluminum and arsenic protect against pitting, dezincification, and scaling.

Reliable performance in marine and industrial settings: Maintains mechanical integrity under fluctuating thermal loads and flow conditions.

High thermal conductivity for effective heat transfer: Ensures energy-efficient operation.

Extended service life: Reduces maintenance costs and unplanned downtime.

Compliance with international standards: Manufactured to meet ASTM B111, ASTM B395, and ASME SB111/SB395.

Mechanical Properties (Annealed – Temper O61):

Aluminum improves corrosion resistance, strength, and dezincification resistance. Adding 1.8-2.5% aluminum to brass creates a protective aluminum oxide film on the surface, which resists attack in aggressive environments like seawater. Aluminum also increases the alloy's strength without sacrificing ductility.

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Q1: What is C68700 used for?

A: C68700 is used for condenser tubes and heat exchangers in high-velocity seawater. Specifically, ASTM B111 C68700 tubes are installed in power plant condensers, desalination plants, marine vessels, and industrial cooling systems handling saltwater or brackish water.

Q2: What is the difference between C68700 and C44300?

A: C68700 offers better resistance to high-velocity seawater impingement than C44300. C68700 contains aluminum and arsenic for turbulent flow conditions. C44300 contains tin and is suited for contaminated but lower-velocity water.

Q3: What is the European equivalent grade for UNS C68700?

A: The European equivalent for UNS C68700 is CuZn22Al2 (DIN 17660) or CW702R. These designations share the same composition: Cu 76-79%, Al 1.8-2.5%, As 0.02-0.10%.

Q4: What is the Chinese equivalent grade for ASTM B111 C68700?

A: The Chinese equivalent for ASTM B111 C68700 is HAl77-2 per YS/T 649-2018. HAl77-2 has identical requirements: Cu 76-79%, Al 1.8-2.5%, As 0.02-0.10%.

Q5: What is the thermal conductivity of C68700?

A: The thermal conductivity of C68700 is 109 W/(m·K) at 20°C. ASTM B111 C68700 tubes achieve a heat transfer coefficient of ≥5200 W/m²·K, approximately 30% higher than stainless steel.

Q6: What is the recommended hot working temperature for C68700?

A: The recommended hot working temperature for C68700 is 750–830°C. Finish working above 550°C. Control oxygen at 0.5-1.5% to prevent zinc volatilization and hot cracking.

Q7: What is the difference between annealed (O61) and hard temper C68700?

A: Annealed C68700 (O61) has 345 MPa tensile strength and ≥50% elongation. Hard temper C68700 (H04) has 600 MPa tensile strength but only 10% elongation. For forming, always use annealed C68700.

Q8: Can C68700 be used for potable water?

A: No, C68700 is not recommended for potable water. Due to arsenic content (0.02-0.10%), C68700 poses a leaching risk. Use C12200 (DHP copper) for drinking water applications.

Q9: What welding process is recommended for C68700?

A: TIG welding with CuAl8 (ERCuAl-A1) filler metal is recommended for C68700. Use 80-120A current, preheat to 150°C, and maintain argon purity ≥99.99% to prevent arsenic-induced porosity.

Q10: How does the cost of C68700 compare to titanium?

A: C68700 costs approximately 40% less than titanium or cupronickel C70600. Despite lower cost, C68700 provides a comparable service life of >15 years in seawater.

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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