Aluminum Brass or C70600 for Heat Exchanger

C70600 contains no zinc. Aluminum brass contains about 22% zinc, which is the source of its dezincification problems in heat exchanger service.

Key difference for heat exchanger tubes：

C70600 ： zinc is an impurity (0.5% max). No dezincification risk inside your heat exchanger.

Aluminum brass ： zinc is a major alloying element (20-23%). Dezincification is a real risk, especially in warm or stagnant zones.

Zinc is the problem. C70600 has almost none. Aluminum brass is full of it. For long heat exchanger life, less zinc is better.

C70600 outperforms aluminum brass in most heat exchanger conditions, especially at higher temperatures and velocities.

Where aluminum brass still works in heat exchangers：

Cool seawater (under 40°C)

Low velocity (under 1.5 m/s)

Clean, well‑treated seawater

Intermittent operation (not continuous)

Where aluminum brass fails in heat exchangers：

Warm seawater (above 50°C)

Higher velocity (above 2.0 m/s)

Stagnant or low flow areas near tube sheets

Polluted or stagnant seawater

Dezincification is a type of corrosion where zinc is selectively removed from the alloy, leaving behind weak, porous copper that cannot hold pressure. Aluminum brass contains 20-23% zinc, so heat exchanger tubes made from it are vulnerable.

How dezincification happens in a heat exchanger：

Warm seawater attacks the zinc in the tube wall

Zinc dissolves and leaches out of the tube

What remains is a weak, spongy copper structure

The tube loses strength and may leak or burst under pressure

Why C70600 heat exchanger tubes do not dezincify：

Zinc is an impurity, not a major alloying element

Maximum zinc is 0.5%

Even if all zinc leached out, it would not affect tube strength

Signs of dezincification in heat exchanger tubes：

Tube wall turns reddish (copper color) where it should be yellow‑brass

Tubes feel soft and can be crushed by hand during retubing

Pinhole leaks appear without obvious external pitting

Both alloys have similar thermal conductivity. But C70600 stays cleaner over time, so its heat transfer actually lasts longer.

Why the higher conductivity of aluminum brass does not always win：

Aluminum brass has higher thermal conductivity on paper

But dezincification creates porous, weak layers that block heat transfer

Biofouling attaches more easily to aluminum brass

A clean C70600 tube often outperforms a partially corroded aluminum brass tube

Real heat exchanger example：

A large shell and tube heat exchanger has 2,000 tubes

Aluminum brass bundle costs 40,000.C70600bundlecosts40,000.C70600bundlecosts52,000.

Aluminum brass lasts 8 years. C70600 lasts 24 years.

24‑year cost： C70600 = 52,000(onebundle).Aluminumbrass=52,000(onebundle).Aluminumbrass=120,000 (three bundles).

Retube with C70600 if your heat exchanger has any of these conditions： warm seawater, higher flow, frequent failures, or a long remaining life requirement.

Retube with aluminum brass only if：

The heat exchanger operates in cool seawater (under 40°C)

Flow velocity is low (under 1.5 m/s)

The heat exchanger has less than 5-10 years of life remaining

Your budget absolutely cannot cover the C70600 upfront cost

Retube with C70600 if：

Seawater temperature exceeds 40-50°C

Flow velocity is above 1.5-2.0 m/s

You have had dezincification failures before

The heat exchanger needs to run for 15-20 more years

You want to stop retubing every 5-8 years

What you need to check before upgrading：

Tube sheet hole diameter (same OD, fits)

Rolling procedure (C70600 is slightly stiffer)

Gasket materials (compatible)

Q1： Which is better for heat exchanger tubes, C70600 or aluminum brass?

C70600 is better for most heat exchanger applications. It resists warm seawater, handles higher velocities, and does not dezincify. Aluminum brass works only in cool, low velocity, clean conditions. If your heat exchanger runs in warm seawater (above 40-50°C) or has failed before, choose C70600.

Q2： What is dezincification and does it happen in heat exchanger tubes?

Dezincification is the selective removal of zinc from brass. It leaves behind weak, porous copper that leaks. Aluminum brass heat exchanger tubes contain 20-23% zinc, so they are vulnerable. C70600 contains almost no zinc (0.5% max), so it does not dezincify. This is the #1 reason heat exchanger owners replace aluminum brass with C70600.

Q3： Can I replace aluminum brass tubes with C70600 in my existing heat exchanger?

Yes, in most cases. The OD is the same, so the tube sheet holes fit. Check wall thickness (may differ slightly). Adjust rolling procedures (C70600 is a bit stiffer). Get engineering approval. Many heat exchanger owners have done this successfully. You will not need to modify the tube sheet.

Q4： Which alloy handles higher flow velocity inside heat exchanger tubes?

C70600 handles higher velocity. Aluminum brass safe limit is about 1.5-2.0 m/s. C70600 safe limit is 2.5 m/s. At velocities above 2.0 m/s, aluminum brass loses its protective film. Impingement corrosion starts at tube inlets. If your heat exchanger runs at 2.0-2.5 m/s, you need C70600.

Q5： Is aluminum brass cheaper than C70600 for heat exchanger tubes?

Yes, aluminum brass tube is typically 20-40% cheaper than C70600. However, you may replace aluminum brass tubes 2-3 times during the life of one C70600 bundle. The initial saving disappears quickly. For a heat exchanger that runs for 20 years, C70600 is usually cheaper overall.

Q6： Does aluminum brass resist biofouling in heat exchangers as well as C70600?

Aluminum brass releases copper ions like C70600, but less effectively because of its lower copper content (76% vs 88%). In heat exchanger service, C70600 resists barnacle and mussel attachment better. For heat exchangers that cannot be cleaned frequently, C70600 is the better choice.

Q7： Can aluminum brass be used in warm seawater heat exchangers?

Not recommended. Warm seawater (above 50°C) accelerates dezincification in aluminum brass. C70600 performs well up to 60°C. If your heat exchanger sees warm seawater (tropical locations, power plant discharge, recirculating systems), C70600 is the safer choice.

Q8： Which material is easier to roll into heat exchanger tube sheets?

Both are rollable. Aluminum brass is slightly softer, so it expands more easily. C70600 is a bit stiffer but still easy to roll in annealed temper. Most tube sheet rolling tools work for both. Adjust your rolling torque slightly higher for C70600.

Q9： Does aluminum brass require inhibitors like arsenic for heat exchanger service?

Yes, aluminum brass for seawater heat exchangers is typically made with 0.02-0.10% arsenic. The arsenic inhibits dezincification. Without arsenic, aluminum brass fails quickly. C70600 does not require any inhibitor. The alloy is inherently resistant to dezincification.

Q10： Which alloy has better thermal conductivity for heat exchangers?

Aluminum brass has higher thermal conductivity on paper (about 100 W/m·K vs 45 W/m·K for C70600). However, dezincification creates porous layers that block heat transfer. Biofouling attaches more easily to aluminum brass. A clean C70600 tube often outperforms a partially corroded aluminum brass tube in real service.

Q11： Is aluminum brass still available for heat exchanger tube orders?

Yes, but mills produce less of it than they did 30 years ago. Most production has shifted to C70600. Lead times may be longer. Prices may be less competitive. For many heat exchanger tube sizes, C70600 is now easier to get and sometimes similar in price.

Q12： Should I upgrade from aluminum brass to C70600 when retubing my heat exchanger?

Yes, in most cases. Calculate the lifecycle cost. Factor in tube cost, labor, and lost production during shutdowns. For most heat exchanger owners, C70600 pays for itself after one or two replacement cycles. If your heat exchanger fails every 5-8 years, upgrading to C70600 will save you money and downtime.

First, chemistry. We put a sample in our spectrometer (ASTM E1473). Nickel has to be between 9% and 11%. Iron between 1% and 1.8%. If it's off, the whole melt is rejected. No argument.

Then mechanical. One tube per heat gets pulled until it breaks (ASTM E8). Must hit 310 MPa. We also flatten a ring. Squeeze it to three times the wall. If it cracks, reject. Flare a sample with a 30° cone. If it splits, reject.

Then eddy current. This is 100% of tubes. A probe goes through every single tube (ASTM E243). Any signal above the line, the tube is out. No patching. No "good enough".

You get a Mill Test Report with every order. Heat number on every tube. If you want SGS or BV to watch, we can set that up.

Each tube gets plastic caps on both ends. Keeps dirt and water out. Between layers, we put VCI paper. Stops rust from condensation during the long boat ride.

Each bundle gets shrink wrapped. That seals out moisture. Then steel straps, four to six per bundle. For small tubes or cut lengths, we use wooden cases. For standard 6m tubes, steel straps on a wooden pallet.

The label is waterproof. It shows grade (C70600 / 90/10), size (OD x BWG), heat number, quantity, and length.

Before the container closes, we take photos and tape the packing list inside the door. We send you the photos.

Three melting furnaces, 5 tons each. Copper, nickel, iron go in. Liquid alloy comes out.

Two casting lines pour that liquid into solid billet. 80mm to 220mm across.

Two extrusion presses (2500T and 3500T) punch a hole through the billet. Now it's a hollow shell.

Four pilger mills roll the shell down. Smaller diameter, smoother surface.

Eight drawing benches pull the tube through dies. This gets the exact OD and wall thickness you asked for.

Four annealing furnaces heat the tube to 600°C. That softens it so you can bend it and roll it into tube sheets.

Three straightening and cutting lines make the tube straight and cut it to your length.

Two eddy current machines check every tube before packing.

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