Roughly 75% of all aluminum ever produced is still in use today. This is not only because the metal is highly recyclable, but it’s also a testament to aluminum’s ability to withstand corrosion. Aluminum is the most recyclable material used in multiple industries. It holds its value and is a vital part of most supply chain logistics. Aluminum is a part of our everyday lives, from our soda cans to our cars and buildings we can’t go a day without coming into contact with or utilizing something that is made from Aluminum.
Aluminum’s resilience, malleability, and robust application possibilities have made it a staple in facades, exterior/interior applications, roofing, and so much more. But like other traditional metal building materials, aluminum suffers from the same fate of rust or corrosion, right? The reality is: aluminum does not rust, but it does corrode.
What exactly is the difference between corrosion and rust, and how does corrosion affect aluminum compared to rust’s effects on other materials?
What is Corrosion?
Corrosion is usually defined as the degradation of metals due to an electrochemical process. The formation of rust on iron, tarnish on silver, and the blue-green patina that develops on copper are all examples of corrosion.
The most common kinds of corrosion result from electrochemical reactions. General corrosion occurs when most or all of the atoms on the same metal surface are oxidized, damaging the entire surface. Most metals are easily oxidized: they tend to lose electrons to oxygen (and other substances) in the air or in water. As oxygen is reduced (gains electrons), it forms an oxide with the metal.
Corrosion is a dangerous and extremely costly problem. Because of it, buildings and bridges can collapse, oil pipelines break, chemical plants leak, and bathrooms flood. Corroded electrical contacts can cause fires and other problems, corroded medical implants may lead to blood poisoning, and air pollution has caused corrosion damage to works of art around the world. Corrosion threatens the safe disposal of radioactive waste that must be stored in containers for tens of thousands of years.
How Does Corrosion Affect Aluminum?
When discussing how corrosion affects aluminum, it’s important to note that there are three key types of aluminum corrosion that can occur:
Atmospheric Aluminum Corrosion: The most common type of corrosion in aluminum, this occurs when aluminum is directly exposed to natural elements. Heavy amounts of moisture in the air can slowly impact the performance of aluminum over time, as well as proximity to saltwater, pollutants, precipitation, wind speed, and temperature. Aluminum’s oxide layer defends against corrosive environments, ensuring that it can continue its effectiveness for a longer period of time versus other traditional metals.
Galvanic Corrosion: The process of galvanic corrosion occurs when aluminum is connected to another metal via an electrolyte (i.e. salt water), causing one metal to completely corrode away while the other is left unharmed.
Uniform Corrosion: Uniform corrosion is a type of corrosion where the metal corrodes evenly over the entire surface. This can be caused by many factors, including exposure to the environment, chemical reactions, and electrochemical processes. uniform corrosion is often difficult to detect in its early stages, as it progresses slowly and evenly. However, if left unchecked, it can cause significant damage to metal surfaces. uniform corrosion can be prevented through the use of corrosion-resistant materials and coatings, as well as regular maintenance and inspection.
Pitting Corrosion: Pitting corrosion is a type of corrosion that occurs when small pits form on the surface of a metal. The pits are usually evenly spaced and have a symmetrical shape. Pitting corrosion can occur on any metal, but it is most common on iron and steel. Pitting corrosion is caused by the action of an electrolyte, such as water or salt, on the metal surface. When an electrolyte comes into contact with the metal, it causes a chemical reaction that creates electrical current. This current causes the metal to corrode, forming pits on the surface. Pitting corrosion can be prevented by using a coating or paint to protect the metal surface from the action of an electrolyte.
Can Aluminum Rust?
Rusting is a form of corrosion that’s specific to iron and steel (because it contains iron). In fact, rust is the common name for iron oxide, when iron or steel bonds with oxygen and undergoes oxidation. Therefore, aluminum can’t rust.
What is the timeframe for Aluminum Oxidation?
Aluminum oxidation happens at a faster rate than steel oxidation because aluminum has a stronger “liking” for oxygen. When all the aluminum atoms have bonded with oxygen, the oxidation process stops. This process can take seconds to form 1.5nm-2nm, and anywhere between one month and one year for anywhere between 2nm-4nm if left completely unchecked.
How Can You Identify Aluminum Corrosion?
Unlike iron that flakes through when it corrodes, aluminum oxide forms a hard, white-tinted surface skin. Aluminum corrosion is known as aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. Aluminum oxide corrosion also looks a lot more like aluminum (dull gray to powdery white in color), so it isn’t as easy to notice as rusted iron.
How Can You Identify Aluminum Corrosion?
Aluminum corrosion can appear visibly in various forms. You’ll usually find a blue/teal hue with the typical rusting color covering the aluminum. In other instances, you could find visible signs of deep greens, holes known as pitting, “rocky” outcroppings, or small dark splotches.
How to Treat Bare Aluminum
That aluminum oxidation can protect bare aluminum indefinitely, but if you want to paint the aluminum you’ll need to sand off the aluminum oxide coating and get to clean aluminum. This is because most commercial coatings don’t adhere well to aluminum oxide. Your paint job won’t last long on any aluminum surface if you haven’t sanded and cleaned it thoroughly prior to painting. Make sure to find a metal primer specifically designed for aluminum surfaces as well, since most basic primers and paints are not designed for this application.
How Do You Stop Aluminum Corrosion?
Since aluminum so readily bonds with oxygen, there’s little that can be done about aluminum oxidation. Aluminum corrosion, however, can be a serious problem. To prevent aluminum corrosion, you should consider:
- First and foremost, choosing the correct alloy: some alloys have better corrosion-resistance than others.
- Applying a protective coating
- Minimizing the effect of galvanic corrosion. Galvanic corrosion is caused by putting two dissimilar metals, like aluminum and steel, next to each other.
- Paint – provides a moisture-proof barrier
- Powder coat
If you’ve found yourself asking “does aluminum rust?”, then the answer is (technically) no! Looking for high-quality aluminum products? Wieland-Wrisco has you covered. We have decades of providing the finest-quality aluminum products to our clients. We are your go-to for all prefinished aluminum sheets, custom-painted aluminum, and much more. Contact us today HERE and see why Wricsto is the best provider of aluminum products in the country.