Aluminum vs Steel: Which Metal Is Better?

Steel vs aluminum differ in many aspects aside from the noticeable weight difference. Such differences result in varying uses for these metals.

Among the qualities that aluminum vs steel differ from are malleability and strength. Steel may offer higher tensile strength, while aluminum guarantees outstanding machinability. Aluminum also resists corrosion better than steel but is more expensive.

We give you a more comprehensive aluminum vs steel comparison below. Tune in to know which is better for your specific metalworks.

The Difference Between Steel vs Aluminum

You can tell steel vs aluminum differ by holding them side by side. There's a clear contrast both in weight and texture. And it's the elemental composition of the two influencing this.

As you may already know, steel is an alloy of iron and carbon mixed with other alloying elements. The carbon content can reach up to 2% in weight. You can produce specific qualities of steel by varying the carbon composition. But while carbon strengthens steel, putting too much will make it brittle.

Aluminum alloy is exactly as it sounds. Aluminum is the base component combined with alloying elements such as magnesium. Magnesium produces a light and strong aluminum alloy.

Let's continue to look deeper into carbon steel vs aluminum below.

Corrosion Resistance

One significant difference between steel and aluminium is their ability to resist corrosion. Aluminum is the better option in this segment.

A natural oxide coats the aluminum surface, preventing it from rusting. Aluminum doesn't corrode in most environments as its protective layer bans further oxidation. This impermeable barrier develops once the aluminum interacts with the elements.

The metal produces a thin layer of aluminum oxide after making contact with oxygen. And unlike rust, this oxidized layer doesn't flake but bonds to the aluminum surface. Due to this, aluminum no longer needs any protection from extra coating like paint. But, it's important to remember that aluminum may resist most acids but less alkalis.

Galvanic corrosion on aluminum

Aluminum can also decay through galvanic corrosion. This type of corrosion happens between two different metals touching each other. But touching alone isn’t enough to cause this decay. There must be the presence of an electrolyte or conductive solution like seawater.

This can happen between steel and aluminum, with aluminum corroding faster. Some online forum participants suggest using fiberglass or nylon spacers to isolate aluminum. This will break the contact between the metals and prevent galvanic corrosion.

While corrosion resistance is part of aluminum advantages, it is not for steel. Carbon steel can corrode if exposed to moist and abrasive setups. This is why you paint steel to counteract its corrosion vulnerability.

But, when you add at least 10.5% of chromium to steel, you get stainless steel. Unlike carbon steel, stainless steel has remarkable resistance to rust, hence its name. Or you can add a protective zinc coat through galvanizing.

Malleability

The metal can form into various shapes and thin sheets without breaking. A metal is malleable if it can deform and remain intact through compression. It's synonymous with ductility or the ability to bend without breaking through tension.

In steel vs aluminum, the latter wins the malleability comparison. Aluminum is both malleable and ductile. Hence, it is easier to roll into foil and thin wires. You can form aluminum into intricate shapes even in hot or cold states.

Steel is more challenging to bend and work with if it concerns shape-forming. You may twist and shape steel in its hot state, but it'll be vulnerable to breaking if it is in a cold state. The higher tensile strength of steel compromises its elastic properties.

Although you can have a choice of malleable steel through austenitic stainless alloy. This variant is more malleable than carbon steel due to its high nickel content. They are ideal for sinks and water tanks.

Strength

We can subdivide strength classification into tensile, compression, and yield strength. Tensile strength is the highest pulling tension a material can handle before breaking. Compression strength is a material's breaking point from squeezing. Yield strength refers to the highest force tolerable before permanent deformation.

Steel gets all the belts in all these strength tests. Steel is both bulkier and more robust than aluminum. Below are the approximate strength of aluminum vs steel (structural grade):

Tensile Strength

Steel: 58,000 to around 72,000 psi
Aluminum: 13,000 psi

Compressive Strength

Steel: 25,000 psi
Aluminum: 6,000 psi (low strength grade)

Yield Strength

Steel: 36,000 psi
Aluminum: 5,800 psi

When asked the question, "Which is stronger steel or aluminum," the expected answer is steel. And the different strength ratings above would support this. But the conversation changes when we include density in the picture.

Considering identical strength-to-weight ratios, some aluminum variants can hold up against steel. This is why some higher aluminum variants can be a good alternative to common carbon steel.

Weight

Steel is well known as a heavy metal. Aluminum is one of the lightest in the market. The two metals' elemental composition influences this difference big time. Steel's base element is iron, which is heavier than aluminum. Its carbon content also adds up to its density.

In comparison, steel is three times heavier than aluminum. Steel's rigidity and robust nature are the trade-offs of much heavier weight.

Although aluminum is light, this property remains an advantage in some applications. Aluminum retains excellent strength despite its lower density. It offers half the strength of steel at one-third the steel's weight. Hence, you can match some steel's strength by doubling the aluminum material's weight.

If weight is a big concern, aluminum becomes the go-to material for most metalworkers.

Cost

In general terms, steel is less expensive than aluminum. Despite steel being the stronger metal, it is also more common, hence the lower price tag. Its base element is more abundant than aluminum, which comes from bauxite ore. According to the World Economic Forum, almost 94% of metals mined in 2019 are iron ores at 3.04 B tonnes.

In perspective, there were only 347 million tonnes of bauxite ore extracted in the same year. And only 62.9 million tonnes of those are actual aluminum materials.

This makes aluminum three to five times pricier than carbon steel. But, not all types of steel carry a lighter price tag than aluminum. Stainless steel is more expensive due to its better qualities. Additionally, aluminum vs steel prices will vary depending on market conditions. It would help if you also consider the lifecycle cost of each metal. While steel is more affordable, it doesn't last as long as aluminum does.

Aluminum's corrosion resistance compensates for its higher price tag with longer service life. It's also easier to recycle than steel.

Uses

There are rich steel vs aluminum applications everywhere, no doubt. From daily utensils to large machinery, aluminum vs steel is present. Below, we look at their most common uses in the field they are most used in.

Engineering and Construction

Engineering and construction need robust materials. Steel is ideal for foundation and supports throughout the construction process. Beams, girders, posts, and columns are steel-made to support extreme weight.

Aluminum is also a suitable alternative as it's strong but also lightweight. Aluminum is the go-to for building the external facade of a building. It can also used for staircases, shelves, roofs, and windows.

Transportation

Steel vs aluminum is also popular in the transportation industry. Where there is a need for strong and lightweight materials, aluminum is the top choice. It is ideal for fabricating car doors and panels to reduce weight. Aluminum is also critical for building planes and aerospace parts. While recent trends show a shift to aluminum production, steel remains a necessity. This heavyweight metal remains the go-to material for rail tracks and building bridges. And it is still the most common metal for shipbuilding.

Energy

The uses for steel vs aluminum are broader besides them being excellent conductors. For example, steel is the primary material for on and off-shore power generation. Oil rigs and turbines use steel as the main foundational support structure. Transmission towers are also made from high-grade steel to withstand strong forces.

Aluminum is a reliable material for producing electrical components. It also fits the renewable energy section since recycled aluminum is sustainable. Aluminum is best used for manufacturing solar panels and fuel cells.

Conclusion

The practicality of steel and aluminum is undeniable. Both have specific properties ideal for many applications. They also complement what's missing in the other.

The use of steel vs aluminum covers almost every industrial sector. Aluminum reigns when there is a need for a strong and lightweight material.

Steel takes the lead in cases where weight isn't a problem. Steel vs aluminum has so much to offer. It only makes sense that they continue to be popular in various industries. Get the most ideal metal today, and start acing your metalworks!