Steel and aluminum are two of the most widely used materials on the planet.
Aluminum is the second-most abundant metallic element on Earth after silicon, while steel is the world’s most popular alloy.
While both metals have countless uses, there are a few key factors that can help you determine which one is best for the job.
Here’s how they stack up:
CORROSION RESISTANCE
Aluminum oxidizes via the same type of chemical reaction that causes iron to rust. But unlike iron oxide, aluminum oxide sticks to the metal, shielding it from decay. As a result, it requires no paint or other coating to keep it from rusting.
Steel — or carbon (not stainless) steel, to be specific — typically needs to be painted after being spun in order to protect it from rust and corrosion. Zinc is often used to protect against corrosion through the galvanizing process.
MALLEABILITY
While steel is extremely durable and resilient, aluminum is considerably more flexible and elastic.
Aluminum’s malleability and smooth fabrication allow it to form deep, intricate, and precise spinnings, giving handlers significant design freedom. Steel is more rigid and will crack or rip if pushed too far during the spinning process.
STRENGTH
Despite being at risk for corrosion, steel is still harder than aluminum.
While aluminum does increase in strength in colder environments, it is generally more prone to dents and scratches than steel.
Steel is less likely to warp or bend from weight, force, or heat. These resistant properties make it one of the most durable industrial materials.
WEIGHT
Steel’s superior strength also comes with a weight/density that is 2.5 times that of aluminum. It weighs approximately 60 percent less than concrete, however, making it easier to transport and use in various construction and fabrication applications.
With that said, shape and structural rigidity can contribute significantly to the strength of a structure, and when those two factors are optimized, aluminum can provide similar reliability to a comparable steel structure at half the weight.
For example, there is a rule of thumb in boat building that aluminum is roughly half the strength of steel at one-third the weight. This means that an aluminum vessel can be built at a given strength that is two-thirds the weight of a comparable steel boat.
COST
The cost of aluminum and steel is constantly in flux based on global supply and demand, related fuel costs, and the iron and bauxite ore market. Even with that fluctuation, however, a pound of steel is typically cheaper than a pound of aluminum.
USES
A good way to determine whether steel or aluminum is best for a particular application is to take a glance at how the two metals are being used:
Construction
Steel’s strength makes it a prime choice for the bones of many construction projects. It’s a go-to material for skyscrapers, stadiums, railways, roads, airports, steel-made stairs, and other projects where durability is key. Many of the tools used for these projects are made from steel, as well.
Aluminum is also a solid material for stairs, as well as shapes that can’t be created with steel or wood. Aluminum’s strength-to-weight ratio makes it a solid and time-saving material for the construction of high-rise buildings.
Energy
Steel frameworks are key for nuclear power, natural gas, wind power, and electric infrastructure. Steel is also used in offshore platforms, transmission towers, transformer cores, and electromagnetic shields, as well as for extraction and production devices like cranes and forklifts.
Aluminum’s low density and high thermal conductivity make it a great option for electrical transmission lines. Not only is it cheaper than copper, but it is nearly twice as good a conductor and can be formed into wires more easily.
Transportation
In addition to accounting for roughly half of the average car or truck, steel permeates rails, jet engine components, marine vessels, anchor chains, and other high-strength transportation elements.
Aerospace is aluminum’s leading transportation market, with aircraft and spacecraft containing up to 90% aluminum alloys. The demand for increased fuel efficiency has made aluminum an increasingly popular metal in the automotive industry, as well, with aluminum content in modern vehicles projected to grow by more than 60% within the next decade.
Packaging and Consumer Goods
More than half of the weight of household appliances like refrigerators, ovens, and washing machines comes from steel. Steel is also popular for use in metal stairs, screws, nails, and other construction materials.
Aluminum’s non-toxic properties make it ideal for prepackaged foods, medications, and beverages. It is also widely used in making foils and kitchen utensils and is an integral part of countless electronics, including smartphones, televisions, computers, and LED bulbs.
WHICH METAL GETS THE MEDAL?
As we mentioned, a pound of steel will almost always be cheaper than a pound of aluminum. That’s about as close as there is to a clear-cut winner, however. Simply put, the best metal is the best metal for a particular job.
Consider the characteristics of the specific application as much as — if not more — than cost when choosing the best metal for your next project.
