The short answer: no, aluminum does not rust. However, aluminum does and will corrode. What is the difference between rust and corrosion? This is a reasonable question because rust and corrosion are often used interchangeably, but they’re not the same. Corrosion, generally, is a broad reference to the wearing away of metal caused by a chemical reaction. Rust is a type of corrosion referring specifically to the oxidation of iron or steel caused by interaction with water or moisture. Steel rust, as most know, causes the metal to flake away, exposing new steel. The process starts over and goes round and round until the steel is basically eroded back to a more natural state.
However, since aluminum doesn’t contain iron or steel, it doesn’t rust away in most conditions. But aluminum, when exposed to water and oxygen will very quickly corrode. Most can identify rusted steel from its familiar orange color. Aluminum corrosion actually looks white.
The process of aluminum corrosion is known as oxidation. The resulting aluminum oxide is a thin, hard layer that actually protects the metal from further corrosion.
Aluminum oxide appears as a powdery white or dull gray coating. As oxidation occurs, it hardens and creates a protective layer over the newly exposed areas of corroded aluminum. The aluminum corrosion process is actually halted by oxidation—the metal won’t continue to deteriorate unless the aluminum oxide is removed. As mentioned earlier, unlike rust, which has a flaky, orange appearance, aluminum oxidation cannot be easily chipped off the metal surface.
Aluminum oxidation occurs at different rates depending on the type of aluminum, the finish and the environment surrounding the aluminum. Aluminum 5052, for example, is sometimes called The Hulk of aluminum alloys due to its durability and excellent corrosion resistance.
Aluminum 3003, the most widely-used of aluminum alloys, is also particularly good at resisting corrosion, but less favorable to anodizing, a factory process that mimics the natural process of oxidation to create a more durable metal with a corrosion-resistant aluminum finish.
Depending on the environment, aluminum can be a fantastic choice for fabrication jobs that require long durability. Aluminum is used extensively for architectural projects since most of that material is exposed to the outside elements.
When aluminum is combined with some kind of finish, like painting or anodizing, it really becomes an outstanding product because it is so durable.
Not many years ago, I stumbled onto a job where someone had used steel railing and steel perforated infill panels. Powder-coated steel railing, is a popular choice, particularly in residential use. It holds up fairly well, but in this case, because of the perforated holes, there were many pin-hole places where the paint did not adequately cover the metal.
Since rust spreads and grows, this handrail quickly became victim to Mother Nature and the railing looked quite awful.
If the contractor and owner would have selected perforated panels made from painted aluminum, they would have avoided the problem. The pin holes, for the most part, would have self-healed, so-to-speak, and the powder paint would not have failed so horribly.
Many fabrication shops shy away from aluminum because it is hard to cut, form and weld.
Aluminum welding, especially, terrifies many traditional metal job shops. Welding aluminum takes very specific skills and is much more challenging to weld than traditional steel. [TIG Welding]
Still, it is no coincidence that boats, docks, marine products, outdoor products and outdoor architectural products are manufactured from aluminum.
Aluminum is durable, light weight, and, as we have learned, very resistant to corrosion failure.
That is not to say that aluminum is invincible. Chlorides, sulfides and galvanic reactions are typically known as aluminum kryptonite. These kinds of chemical reactions will decimate aluminum very quickly.
Again, aluminum, working in conjunction with some layer of paint or top coat, can effectively cancel some of the elements that like to attack, but, as always, professional engineering and good experience are great ways to determine if you have a project that would excel using aluminum.
All Metals Fabrication excels in aluminum fabrication. We have fabricated light-rail train components, railing, steeples, sun shades, boat parts and much more—all from aluminum.
Learn more about aluminum fabrication and aluminum durability by emailing us at firstname.lastname@example.org.