At a glance, aluminum and stainless steel seem very similar.
From the car in your garage or kitchen in your home to the industries and worksites throughout your city, there’s a good chance one or both metals are hard at work near you.
But which metal is best for your needs?
In this comparison guide, we’ll look at the range of characteristics aluminum and stainless steel share–as well as how they differ–to help you determine the best material for your project, process, or need.
Which is Stronger? Stainless Steel or Aluminum?
Stainless steel will always provide greater strength than aluminum when compared to similar shapes, thicknesses, or designs.
An effective way to compare this is by looking at the tensile strength of each material.
Tensile strength is the resistance of a material to breaking under tension. Exact figures will vary by the alloy in use.
The tensile strength of stainless steel alloys typically starts around 515 megapascals (MPa) and can reach as high as 1300 megapascals (MPa) in some cases.
Aluminum tensile strengths start around 100 megapascals (MPa) and peak around 400 megapascals (MPa).
Through treatment, both alloys can see further increases.
However, based purely on potential, stainless steel will always win when high strength is a priority.
Is Stainless Steel Heavier than Aluminum?
This is one of the critical areas where aluminum offers a distinct advantage.
In most cases, a component made with aluminum will weigh roughly one-third of the weight of an identical component made with stainless steel.
Again, the exact figures will vary based on the specific alloys in question and can be influenced by design choices.
But in all cases, aluminum is measurably lighter than stainless steel.
How Malleable are Stainless Steel and Aluminum?
If you need to create customized shapes or components, the ability to form, shape, and otherwise manipulate your materials is a critical factor to consider.
This is one area where aluminum’s reduced tensile strength becomes a benefit, making aluminum much easier to form, cut, press, bend, or otherwise shape than stainless steel.
If you want a malleable stainless steel option, consider austenitic grades.
These contain higher amounts of nickel, making them more formable for larger objects like sinks, basins, and tanks.
Is Aluminum as Corrosion Resistant as Stainless Steel?
Both stainless steel and aluminum offer excellent corrosion resistance when exposed to water or other mostly neutral fluids.
Much like the chromium oxide layer on stainless steel, aluminum can form a passive aluminum oxide layer to help reduce corrosion risks.
Also, since aluminum contains no iron, it cannot rust.
However, when dealing with more aggressive corrosion risks, such as using highly acidic or basic substances or in marine environments, stainless steel typically offers stronger corrosion resistance.
Exposing aluminum to highly acidic or basic conditions can lead to rapid corrosion and catastrophic failure in most cases.
There are marine-grade aluminum alloys that provide better corrosion resistance against chlorides if lightweight maritime options are needed, but in most cases, stainless will be the dependable choice for long-lasting performance in a broader variety of applications.
Anodizing aluminum can also increase corrosion resistance at an increased cost and often requires more delicate or specialized maintenance to sustain the anodized layer.
You should never anodize stainless steel as the process can degrade the surface of your stainless causing more harm than good!
NOTE: You should also avoid mixing stainless steel and aluminum in scenarios where galvanic corrosion is possible. As the less noble metal, the presence of stainless steel in a galvanic cell can cause aluminum to corrode and fail at a shockingly fast rate.
Is Stainless Steel or Aluminum the Better Electrical Conductor?
While actual performance will vary depending on the alloy in use, the form used, and the environmental conditions, aluminum consistently outperforms stainless for electrical conductivity tests when using similar shapes and applications.
When drawn into a wire, aluminum even competes with copper for conductivity while doing so at a much more affordable price point!
How Well Do Stainless Steel or Aluminum Conduct Heat?
The answer to this question is tricky as it likely depends on the scenario or application.
From a conduction and heat transfer standpoint, aluminum wins easily.
However, aluminum’s melting point is far lower than even the softest grade of stainless steel.
Most aluminum alloys will become dangerously soft at around 400C (roughly 750F), whereas the melting point of 304 stainless steel sits around 1400C (roughly 2550F).
While stainless steel will likely soften before this melting point, this still provides at least twice (and possibly) three times greater temperature tolerance than aluminum.
Yet, stainless steel doesn’t conduct heat nearly as well.
This makes it less ideal for applications where temperatures are not as high, but rapid heat dissipation is preferred.
Possible scenarios might include automotive radiators, electronic heatsinks, or HVAC components.
Understanding temperature tolerances and requirements will be essential to choosing the proper metal because both offer unique operating characteristics.
Can You Weld Stainless Steel and Aluminum?
Yes! However, the reduced heat tolerance of aluminum makes it much more difficult to weld.
The oxidation layer has a much higher melting point than the underlying metal and welds are very prone to bubbling and impurities.
Also, as aluminum is often used in thin sheets, welds must avoid cutting through the material while still ensuring enough penetration to create strong welds.
Due to these added complexities, aluminum welding is considered a specialized skill.
Welding stainless steel is much easier, with improved thermal tolerances and far less sensitivity.
However, you must still take care to avoid weld decay and be wary of warping on thinner stainless components.
Pickling treatments also offer flexibility in healing some of the stress and damage caused by heat exposure when welding if required.
Are Stainless Steel or Aluminum Magnetic?
If you are looking for a metal that won’t respond to magnets, all aluminum forms should fit the bill as the metal and all of its alloys are free from iron.
The magnetic properties of stainless steel alloys will vary.
All ferritic grades of stainless steel will exhibit magnetism to some degree.
Other grades will vary based on the exact metallurgic makeup.
Popular non-magnetic grades of stainless steel include 304 and 904L.
Is Stainless Steel or Aluminum Better for Food Service Use?
Both of these metals are workhorses in the modern kitchen.
Aluminum offers better heat conduction for pots and pans, while stainless offers ultra-durable, easy-to-clean surfaces and appliances.
They’re both present in nearly any kitchen in some way.
If you get down to ultra-specific considerations, stainless steel is less reactive with foods and other products used in the kitchen.
It’s also less porous, making clean up even more straightforward.
Related Guide: Stainless Steel Use in the Food Service Industry
Is Aluminum or Stainless Steel More Popular for Medical Use?
In almost all cases, stainless steel will win out over aluminum in the medical environment.
Medical uses, such as equipment, tools, or even implants, require long-lasting performance and easy to clean surfaces.
Whether you’re talking about scalpels or surgical theatre surfaces, you’re likely to see stainless in use nearly everywhere.
Aluminum’s soft nature makes it less reliable for knife edges or needles, while its porousness makes it less suited to sterilization and easy cleanup over time.
Related Guide: Effective Stainless Steel Usage in Medical Environments
Does Stainless Steel Cost More Than Aluminum?
It’s hard to say.
Prices fluctuate quite a lot depending on global conditions and supply and demand.
While not always the case, the recyclability and ample supply of steel and stainless steel mean it will typically be cheaper when looking at secondary sources or recycled steel.
Aluminum processing and refinement are also very electricity-intensive, so power markets can also influence prices quite severely.
The numbers will likely look very different depending on your approach as well.
By weight, aluminum might appear more expensive.
But aluminum weighs significantly less than steel.
So be sure to consider pricing by volume or component to get an accurate look at the overall costs before making any decisions.
Common Grades & Applications for Stainless Steel
Common aluminum grades include 2024, 5052, 6061, 6063, and 7075.
For marine use, 5052 offers respectable corrosion resistance while keeping the weight low.
Common stainless steel grades vary by industry.
However, 304, 316, and other austenitic grades are most popular due to their excellent balance of strength, corrosion resistance and cost.
Grades 430 and 434 are popular ferritic stainless steel options, while 420 grade stainless steel (often in annealed forms) is a popular choice for martensitic stainless steels.
Applications and uses vary widely by industry as well.
Stainless steel is commonly used in a wide range of industries, including:
- Home appliances
- Oil and gas
- Power generation
- Pulp and paper
- Sports equipment
Aluminum is equally popular, with extensive use in:
- Air filtration and movement
- Bulk processing
- Chemical processing
- Oil and gas
- Power generation
- Trucks and trailers
In most cases, you’ll see that industries use both, taking advantage of the strengths of each while avoiding apparent weaknesses.
Uses span everything from massive holding tanks or vehicular body panels to tiny fasteners or pneumatic lines.
So Which Metal is Best for Your Use Case?
Ultimately, as with most metal choices, there isn’t always an obvious right or wrong choice between stainless steel and aluminum.
The outstanding corrosion resistance, easy maintenance, and ample strength of stainless steel make it an ideal choice in a vast range of situations.
Better still, having numerous grades available makes it easier to minimize any weak points and enjoy long-lasting performance.
If you’re not sure where to start, consider these points:
- Aluminum offers rust resistance and weight savings at the cost of strength and general corrosion resistance.
- Stainless steel offers superior corrosion resistance and tensile strength at the cost of added weight.
- When dealing with heat, stainless steel offers better heat tolerance while aluminum offers better heat conductivity. However, aluminum’s lower melting point makes it less applicable in high-temperature applications.
- Welding stainless steel is much easier than welding aluminum due to these thermal traits.
- If you’re looking for a lightweight option for electrical conduction, aluminum offers an excellent balance of conductivity and price.
- When dealing with complex shapes or extensive forming, aluminum will often offer more malleability. However, some austenitic stainless steel can take shaping well without unreasonable force or effort requirements.
- Costs for both metals can fluctuate widely. Be sure to compare grades and prices to get an accurate idea of overall costs and highlight potential cost savings available.
As a leading stainless steel supplier throughout Canada for more than 40 years, Unified Alloy’s extensive selection of stainless parts, components, and materials allows us to serve needs big and small. Contact one of our expert sales analysts today to discuss how we can help serve your business!
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