C68700 Aluminum Brass Tube for Marine Environments

C68700 aluminum brass (CuZn22Al2) is the preferred material for seawater-handling systems, offering a dezincification corrosion rate below 0.025 mm/year and tensile strength of 550–750 MPa. Compared to ordinary brass, it lasts 8 times longer in sulfide-containing seawater and naturally resists biofouling. This guide covers composition, properties, applications, and purchasing tips.

C68700 is a high-performance aluminum brass produced by GNEE (China) according to ASTM B111 standards. Its precise composition creates a unique β-phase microstructure:

Why β-phase matters: This microstructure gives C68700 three critical advantages over standard brass (C27000, C36000):

Dezincification resistance – Aluminum suppresses zinc leaching, preventing porous copper channels

Erosion resistance – Harder surface withstands high-velocity seawater (up to 5.2 m/s)

Stress corrosion cracking resistance – Suitable for ammonia-free marine environments

All data below are verified by ASTM, ISO, and MIL standards:

Certifications: C68700 seamless tubes from GNEE meet ASTM B111, ASME SB111, and U.S. Navy MIL-C-20265.

Verdict: C68700 is the best value for seawater applications – nearly as corrosion-resistant as CuNi 90/10 but at 40–50% lower cost, and far superior to ordinary brass.

GNEE (China) now offers surface nanocrystallization treatment for C68700 tubes. This process:

Refines surface grains to nanometer scale (50–100 nm)

Increases corrosion resistance by an additional 40% (tested per ASTM G48)

Extends service life in aggressive seawater to over 20 years

Has been adopted in third-generation nuclear power plant seawater systems

Buyer tip: For high-sulfide or high-velocity seawater (>4 m/s), specify nano-treated C68700. The extra upfront cost pays back in reduced downtime.

Q1: What is the actual service life of C68700 in seawater?
A: 15–20 years in typical marine applications, over 20 years with nano-treatment.
With a dezincification rate below 0.025 mm/year, a 2 mm wall thickness tube loses less than 0.5 mm after 20 years. In sulfide-containing seawater, it lasts 8 times longer than standard brass. Actual life depends on flow velocity, temperature, and maintenance, but field data from offshore platforms confirm 15+ years.

Q2: Does C68700 require any coating or cathodic protection?
A: No coating is needed – the alloy is naturally protective.
The aluminum content forms a self-healing aluminum oxide film. Copper ions continuously released from the surface suppress biofouling. However, if connected to more noble metals (e.g., stainless steel, titanium), use insulating gaskets to avoid galvanic corrosion.

Q3: Can C68700 be welded or brazed?
A: Yes, but with specific techniques.
It is brazeable using silver-based filler metals (AWS BAg). For welding, gas tungsten arc welding (GTAW) is recommended with C68700 filler rod. Preheat to 150°C and avoid overheating (max interpass 350°C). Post-weld stress relief at 300°C for 1 hour restores corrosion resistance.

Q4: What is the maximum allowable flow velocity for seawater?
A: 5.2 m/s is the critical erosion velocity per ASTM G73.
At velocities below 5.2 m/s, the protective oxide film remains intact. Above this threshold, mechanical erosion removes the film, causing rapid localized attack. For velocities >5 m/s, consider increasing pipe diameter or using C70600 (CuNi 90/10).

Q5: How does C68700 perform in acidic or alkaline environments?
A: Excellent resistance from pH 2 to pH 11.
It withstands dilute sulfuric acid, acetic acid, and seawater (pH 7.5–8.3). For pH below 2 (strong acids) or above 11 (strong caustics), consult GNEE engineers. Avoid ammonia-containing solutions (pH >9 with NH₃) as they cause stress corrosion cracking.

Q6: What certifications does GNEE provide with C68700 tubes?
A: Mill test reports (MTRs) per EN 10204 3.1, plus third-party inspection if requested.
Each shipment includes chemical composition, mechanical properties, hydrostatic test results, and dimensional inspection. GNEE can also arrange SGS, BV, or Lloyds inspection at buyer's cost.

Q7: What is the minimum order quantity (MOQ) from GNEE?
A: MOQ is 500 kg for standard sizes, 200 kg for nano-treated tubes.
GNEE (China) stocks common sizes (OD 12–50 mm, wall 2–5 mm) with no MOQ for sample orders. Lead time: 7–15 days for stock sizes, 20–30 days for custom dimensions.

Q8: How do I prevent galvanic corrosion when connecting C68700 to steel?
A: Use dielectric unions or rubber gaskets.
C68700 is cathodic to carbon steel and anodic to stainless steel. For steel connections, install a non-conductive gasket. For stainless steel (e.g., 316L), C68700 will corrode preferentially – use a zinc sacrificial anode or isolate electrically.

Every batch of C68700 material undergoes a strict multi-step inspection process. Using optical emission spectrometry (OES), we verify the chemical composition - especially the critical aluminum (2.0–3.0%) and arsenic content - to guarantee dezincification corrosion resistance. Tensile testing and Rockwell hardness checks confirm mechanical properties, while hydrostatic and ultrasonic tests ensure leak-free integrity for heat exchanger or condenser tube applications. We also provide full traceability reports, including dimensional, surface roughness, and grain size analyses. All tests are performed in our ISO 17025-accredited lab, ensuring compliance with ASTM B111, ASME SB111, or customer-specific standards.

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

Our factory is equipped with advanced horizontal continuous casting machines, heavy-duty extrusion presses (up to 3,500 tons), and high-accuracy cold drawing lines specifically calibrated for C68700 aluminum brass. To ensure microstructure uniformity and defect-free surfaces, we also employ online eddy current testing systems and automatic cutting & chamfering units. The entire production process is controlled via a central SCADA system, enabling real-time monitoring of parameters like temperature, speed, and lubrication - guaranteeing consistent mechanical properties and dimensional accuracy for every C68700 tube or rod.

Check Today's Stock & Lead Time