What is an alloy aluminum tube pipe?

Confused by what makes an aluminum tube an "alloy" tube or pipe? Selecting the wrong type can lead to failure in your application. It’s aluminum intentionally mixed with other elements.

An alloy aluminum tube or pipe is a hollow cylindrical product made from aluminum that has been combined with other elements like copper, magnesium, silicon, or zinc to enhance specific properties such as strength, corrosion resistance, or machinability, making it suitable for various demanding applications.

At SWA Forging, while our primary focus is on robust forged aluminum rings and discs, we understand the entire ecosystem of aluminum products. Many of our clients who purchase our forgings also utilize alloy aluminum tubes and pipes¹ in their assemblies. The principles of enhancing aluminum's properties through alloying are universal, whether it's for a high-strength forged component or a precisely engineered tube for fluid transfer or structural support. Let's delve into what makes these alloyed tubes special.

What are the different grades of aluminum tubing?

Trying to choose the right aluminum tubing but baffled by all the different grade numbers? Picking an unsuitable grade could compromise your project’s integrity or performance. These grades define specific alloy compositions.

Aluminum tubing comes in various grades, primarily classified by their alloy series (e.g., 1xxx, 3xxx, 5xxx, 6061, 7075). Each grade offers a unique combination of strength, workability, corrosion resistance, and weldability, tailored for different applications.

The world of aluminum tubing is vast, with grades tailored for nearly any application you can imagine. These grades are typically defined by the aluminum alloy series they belong to. Here's a look at some common ones used for tubing:

• 1xxx Series (e.g., 1100): This is essentially commercially pure aluminum. Tubing from this series is soft, highly formable, and has excellent corrosion resistance and electrical conductivity. However, it's not very strong. You might see it in electrical conduit or chemical processing where purity is key.
• 3xxx Series (e.g., 3003): This series is alloyed primarily with manganese. It offers moderate strength – about 20% stronger than the 1xxx series – along with good workability and corrosion resistance. 3003 tubing is common for general-purpose applications like fuel lines, hydraulic tubes (in low-pressure systems), and heat exchangers.
• 5xxx Series (e.g., 5052, 5083, 5086): Magnesium is the principal alloying element here. These alloys are known for good strength (especially after work-hardening), excellent weldability, and outstanding corrosion resistance, particularly in marine environments. 5052 tubing is often used for hydraulic lines, fuel tanks, and marine components.
• 6xxx Series (e.g., 6061, 6063): Alloyed with magnesium and silicon, this series is heat-treatable, offering a great balance of good strength, corrosion resistance, weldability, and extrudability. 6061-T6 tubing is incredibly versatile, used in structural applications, bicycle frames, railings, and pressure vessels. 6063 is often favored for architectural applications due to its excellent surface finish. Many of our forging clients at SWA Forging are familiar with 6061 due to its widespread use.
• 7xxx Series (e.g., 7075): Zinc is the main alloying element, and these are heat-treatable alloys offering the highest strengths among aluminum alloys. 7075 tubing, while more challenging to weld and form, is used in high-stress applications like aircraft structures and high-performance sporting equipment.
  The choice of grade depends entirely on the demands of the application – from simple fluid transport to critical structural support.

Which alloy of aluminium is used in aircraft?

Ever wondered what specific aluminum alloys keep airplanes safely in the sky? The choice isn't random; it involves materials with exceptional performance characteristics. Several key high-strength alloys are favored.

Aircraft construction primarily utilizes high-strength aluminum alloys such as 2024, 6061, and 7075. These alloys are chosen for their superior strength-to-weight ratios, fatigue resistance, and, in some cases, good corrosion resistance after specific treatments.

When it comes to building aircraft, material selection is absolutely critical, and aluminum alloys have been the backbone of aerospace for decades. The primary drivers are the need for lightweight materials that are also incredibly strong and resistant to fatigue. For tubing applications in aircraft, you'll commonly encounter:

• 2024 Alloy: This copper-alloyed aluminum is renowned for its high strength and excellent fatigue resistance, especially in the T3 temper (2024-T3). It's often used for fuselage and wing tension members, as well as hydraulic tubing in high-pressure systems where cyclic loads are significant. Its corrosion resistance isn't as high as some other alloys, so it's often clad with a layer of pure aluminum (Alclad) or otherwise protected.
• 6061 Alloy: This magnesium and silicon alloy, typically in the T6 temper (6061-T6), offers a great all-around combination of good strength, good corrosion resistance, good weldability, and good machinability. It's used for a wide range of aircraft components, including landing gear, fuselage structures, wing components, and various fluid lines where its balance of properties is advantageous. At SWA Forging, we produce many 6061 forged parts, so we're intimately familiar with its reliable performance.
• 7075 Alloy: With zinc as its primary alloying element, 7075 (often in the T6 temper) is one of the highest-strength aluminum alloys available. It's used in critical structural components that experience very high stresses, such as wing spars, fuselage bulkheads, and other highly loaded fittings. While incredibly strong, it can be more susceptible to stress corrosion cracking if not properly designed for and treated, and its weldability is limited.
  The choice among these, and other specialized aerospace alloys, depends on the specific demands of the component – load, fatigue life, operating environment, and manufacturing considerations.

Do Aluminium alloys rust?

Worried about your aluminum parts corroding away like old steel? It's a common concern, but aluminum behaves quite differently from iron-based metals. No, aluminum alloys² do not "rust" in the traditional sense.

No, aluminum alloys do not rust. Rust is specifically iron oxide, which forms on iron or steel. Aluminum does oxidize, forming a protective layer of aluminum oxide that prevents further corrosion in many environments.

This is a really important distinction. The term "rust" specifically refers to the reddish-brown flaky substance (iron oxide) that forms when iron or steel corrodes. Aluminum, being a non-ferrous metal, simply cannot rust.
However, aluminum does react with oxygen in the air. This process is called oxidation. When aluminum oxidizes, it forms a very thin, hard, and tenacious layer of aluminum oxide (Al₂O₃) on its surface. Unlike rust on steel, which is porous and flakes off, exposing fresh metal to further corrosion, this aluminum oxide layer is very dense and strongly adheres to the base aluminum. Crucially, this oxide layer is self-healing; if it gets scratched, fresh aluminum is exposed, which quickly oxidizes to reform the protective barrier. This passive oxide layer is what gives aluminum its excellent natural corrosion resistance³ in many environments.
That said, aluminum alloys can corrode under certain aggressive conditions. For example:

• Galvanic Corrosion: If aluminum is in contact with a more noble metal (like copper or stainless steel) in the presence of an electrolyte (like saltwater), the aluminum can corrode preferentially.
• Aggressive Chemical Environments: Very high or very low pH solutions, or exposure to certain chemicals (like some strong alkalis or chlorides), can break down the protective oxide layer and lead to corrosion.
  Different aluminum alloys also have varying degrees of corrosion resistance. For instance, the 5xxx series alloys (with magnesium) are renowned for their excellent corrosion resistance, especially in marine settings. The 2xxx series (with copper) are generally less corrosion-resistant and often require protective coatings. But the fundamental point remains: aluminum doesn't "rust."

What is the most common aluminum pipe?

Searching for a general-purpose aluminum pipe and wondering which type is the go-to choice? For many standard applications, one particular alloy stands out due to its versatility. Alloy 6061-T6 is exceptionally common.

The most common aluminum pipe (and tube) is arguably made from 6061 alloy, particularly in the T6 temper. Its excellent combination of strength, weldability, corrosion resistance, and machinability makes it suitable for a wide array of structural and fluid-carrying applications.

When people refer to a standard or general-purpose aluminum pipe or tube, they are very often thinking of 6061-T6. There are several reasons for its widespread popularity:

• Good Strength: The T6 temper (solution heat-treated and artificially aged) gives 6061 impressive strength, making it suitable for many structural uses, from frameworks and supports to railings and machine parts.
• Excellent Weldability: 6061 is readily weldable using common techniques like TIG or MIG welding, which is crucial for fabricating complex structures or pipe systems.
• Good Corrosion Resistance: It offers good resistance to atmospheric corrosion and corrosion from many common substances, making it durable in various environments.
• Machinability: It machines well, allowing for threading, drilling, and other finishing operations.
• Extrudability: 6061 extrudes well, making it efficient to produce in standard pipe and tube sizes and shapes.
  Another common alloy, especially for applications where appearance and a smoother finish are more critical than maximum strength, is 6063. It's often used for architectural purposes like window frames, door frames, and decorative trim, but 6061-T6⁴ generally takes the lead for broader industrial and structural pipe applications. At SWA Forging, many of our customers who use our 6061 forged components often pair them with 6061 pipes and tubes in their larger assemblies because the material properties are well-understood and compatible. Its versatility truly makes it a workhorse in the aluminum world.

Conclusion

Alloy aluminum tube and pipe are engineered by adding elements to pure aluminum. This enhances properties like strength and corrosion resistance, tailoring them for specific, often demanding, applications like aircraft structures.