Both aluminum tubing and stainless steel tubing have their strengths and weaknesses. Why might you choose one type of tubing over the other?
Both aluminum and stainless steel are produced on a spectrum of alloys. All of these alloys have different chemical and physical properties.
Generally, stainless steel alloys are categorized into austenitic, ferritic, and martensitic steels. Aluminum is categorized by heat treatability and temper.
So, for your project, which is better: stainless steel or aluminum?
Which Is Better: Stainless Steel or Aluminum?
There are six main factors to consider when debating whether to use stainless or aluminum:
- Conductivity
- Weight
- Strength
- Durability
- Secondary operations
- Cost
Let's start from the top!
1. Steel Vs. Aluminum: Conductivity
Aluminum is a strong conductor, which can be good or bad depending on your application. The 1000-series of aluminum alloys are the best conductors. This series is used to make products like bus conductors.
If you're looking for lower conductivity, steel is the better option for you.
2. Steel Vs. Aluminum: Weight
By volume, steel is three times heavier than aluminum. Again, this can be good or bad depending on your needs. Heavier metals tend to be stronger by default.
If your application is consumer or lightweight (such as kitchen supplies, medical tools, or aerospace) aluminum will provide more ease of use. If your application is structural or otherwise weight-indifferent, steel will do the job at a lower cost.
3. Steel Vs. Aluminum: Strength
As we mentioned above, stainless steel's increased weight comes with increased strength. Steel can withstand higher shock, impact, stress, and pressure than aluminum. It's less likely to bend or give under pressure.
Stainless steel's strength is further increased by its alloy - high carbon steels are harder and sturdier than low-carbon steels. Increased levels of chromium and molybdenum also contribute to overall strength.
4. Steel Vs. Aluminum: Durability
The battle of "aluminum vs. stainless steel: corrosion edition" is not even a close one.
Not only is stainless steel stronger than aluminum, it's also more durable. It's less likely to scratch, and it holds up in highly corrosive environments. Higher chromium and molybdenum percentages also contribute to steel's incredible durability.
Aluminum is simply not as durable as stainless steel. It corrodes much faster (even with finishing) and can't stand up to high-stress environments or applications. Oxidation and corrosion are a bummer for looks, but they also can cause dangerous structural deficiencies.
5. Steel Vs. Aluminum: Secondary Operations
In general, steel has a higher weldability than aluminum. It's easier to weld, and the final welds are more consistent. Steel can be welded with common tools, and doesn't require a lot of experience.
Aluminum is more finicky to weld, and requires more experience.
Stainless steel is also easier to heat treat. Some aluminum alloys are heat treatable, but you should make sure you have the right alloys before requesting it.
6. Steel Vs. Aluminum: Cost
A pound of aluminum is much more expensive than a pound of steel.
This cost isn't as straightforward as you might think. Because aluminum is lighter than steel, you're also getting more material per pound. That means you can produce more units per pound of aluminum vs. per pound of steel.
Per unit produced, the costs can balance out (but don't be surprised if aluminum is ultimately more expensive due to raw material costs!). You'll also need to consider type of alloy in your final cost analysis.
You can learn more about the cost of stainless steel tubing vs. aluminum tubing here.
The Winner? It Depends
Aluminum and stainless steel tube both have a place in CNC tube fabrication. Your choice of material often depends on your application.
If you don't want your component to conduct electricity, go with stainless steel tube fabrication. If corrosion resistance isn't a concern, you can save a few bucks with aluminum tube. See what we mean? These are just two simple examples of making a smart decisions. (Consulting with your manufacturing is a good start, too.)
Now that you've got material choice nailed down, click the graphic below to get a free, handy reference for tubing sizes:
(Editor's note: This article was originally published in August 2016 and was recently updated.)
