In terms of importance, aluminum is probably surpassed only by steel when it comes to industrial metals. That’s because in addition to being one of the most abundant materials on our planet (aluminum is the third most commonly found element in the Earth’s crust), it has a number of benefits that make it extremely attractive to manufacturers and engineers.
First, aluminum is extremely lightweight and has a high strength-to-weight ratio. It’s also quite flexible, being one of the more malleable metals. Aluminum is highly corrosion resistant and easily recyclable, a factor that’s becoming more important as we look for more sustainable solutions and applications. It’s also extremely hygienic, making it an ideal choice for industries where cleanliness is important, like food and beverage containers and medical supplies.
But with all those positive characteristics, we haven’t yet mentioned durability. The truth is that not many people think of aluminum as being particularly durable. Certain aluminum alloys can even be stronger and longer lasting than stainless steel. Aluminum is more durable than most people realize, especially when weight is taken into consideration.
Today we’ll be looking at aluminum’s durability and some things you’ll want to consider when working with a material supplier.
How do we measure the strength of aluminum?
When discussing aluminum’s durability, it’s much stronger than most people realize. This is because when looked at pound for pound, aluminum has an extremely high strength-to-weight ratio. When engineers are measuring and testing the strength and durability of a metal, they look at several distinct mechanical properties. Each of these ways of analyzing strength can be measured separately.
First, compressive strength measures the capacity of a metal or other material to withstand loads pushing down on it. Compressive strength resists any force that is pushing the object in on itself, such as a vice or a heavy load weighing it down.
In contrast, tensile strength looks at how resistant a material is to being pulled apart. When measuring tensile strength, engineers will attempt to determine how much tension a material can withstand as it is being stretched or pulled before it breaks apart altogether. This is useful for looking at how a material can perform in applications that involve hanging or pulling a large amount of weight.
Yield strength is a way of understanding a material’s ability to resist being bent or reshaped. The yield point indicates the moment when nonlinear (elastic + plastic) deformation begins. Any pressure on an object that does not exceed the yield point of the material will deform elastically and then return to its original shape once the stress is removed. When the yield point is surpassed, some amount of deformation will be permanent.
Finally, impact strength tells us the ability of a material to withstand a suddenly applied load. This measurement is determined by either the Izod impact strength test or Charpy impact test, which records the amount of impact energy necessary to fracture an object.
All together, these different criteria tell us how strong an object is.
Is aluminum as strong as steel?
There’s no easy answer to the question of whether aluminum is as strong as steel. There are so many different alloys for both aluminum and steel (with stainless steel being one category of steel alloys) that you really must compare any two alloys directly to each other. Most of the time steel is stronger, but also much heavier.
Simply in terms of hardness, a typical steel alloy is stronger than a typical aluminum alloy (though there definitely are high performance aluminum grades that can match or exceed the strength of steel). Steel is also much denser, so when it comes to strength-to-weight ratio, aluminum is the clear winner.
But this is where we must point out that strength is not the only factor that determines a material’s durability. Durability, broadly defined, is a material’s ability to withstand pressure, wear, and damage. Obviously strength has a lot to do with durability, but it’s certainly not the only consideration.
Corrosion resistance is a big factor in durability
Aluminum offers natural resistance to corrosion, thanks to the very thin oxide layer that forms on its surface. This oxide helps to preempt additional oxidation from occurring. In fact, when the surface of the aluminum takes any damage, the oxide layer repairs itself.
One type of corrosion is known as galvanic corrosion. This happens when there is an electrolytic bridge between two different metals. One of the metals becomes an anode leading to corrosion, and this can happen to aluminum under the right circumstances, so it must be prepared for. Metals, including aluminum, become more susceptible to galvanic corrosion when exposed to chloride, such as in marine environments. Certain aluminum alloys are better at resisting galvanic corrosion, and thus more durable.
Stress corrosion cracking is another failure mode that must be considered. This happens when metal is subjected to tensile stress for an extended amount of time in a corrosive environment. Thankfully, because of aluminum’s high level of corrosion resistance, the risk of stress corrosion cracking is diminished in mildly corrosive environments.
Finally, crevice corrosion is another source of worry for aluminum. This takes place at or near narrow crevices in joined surfaces of a metal product. Again, this is of particular concern in marine environments; care must be taken to properly design the product and consideration must be given to selecting the right alloys.
Your Technical Services Partner
Aluminum is an extremely durable metal, but hopefully this information will help you realize the importance of selecting the right alloy based on your application’s unique requirements. That’s why you need to partner with a supplier who makes it a priority to ensure you get the right material for the job. At Clinton Aluminum, our knowledgeable and friendly sales team is eager to work with you through every step of the procurement process. Contact us today to learn more about which aluminum alloy is right for you.