As oxidation occurs, it hardens and creates a protective layer over the newly exposed areas of corroded aluminum. Unlike rust, which has a flaky, reddish appearance, aluminum oxidation cannot be easily chipped off the metal surface.
It’s a valid question and one that a lot of folks think they have the answer to, but you may be surprised by what I have to tell you about aluminum and its ability to stand up to corrosion. Aluminum is seen as a rockstar of corrosion resistance and is one of the few metals, along with stainless steel, that can hold up to exterior and coastal exposures over long periods of time.
Iron oxide (rust) is a soft red colored metal that begins to expand and flake off as it is chemically transformed which exposes more of the underlying steel or iron to the air and the process continues until the metal is completely transformed to iron oxide. It is actually quite hard and serves as a protective coating around the underlying aluminum.
Used in construction, sports, and a wide variety of other applications, aluminum continues to be used regularly. However, fears of rusting metal seem to steer many people away from using it for DIY projects.
It doesn’t show a brown-bronze color as rust does, which is why most people don’t notice that their aluminum is corroding until it’s too late. Lime and calcium can form as well, both of which cause the color and integrity of aluminum to become dull.
Since the mixture isn’t completely made out of aluminum, you won’t have the same benefits. However, such alloys are generally much tougher and last longer as long as you take care of them properly.
When calcium and other issues start to form, they can get dirty and turn brown. If you’re worried about your aluminum rusting or corroding, then remember that it’s not inevitable; You can take preventative steps so it never oxidizes or starts to deteriorate.
It starts to corrode and grow all sorts of bacteria and other problems. You can buy sprays that can be applied to the surface of the aluminum to prevent it from corroding or getting rust from nearby steel or iron.
Try out the Corrosion Inhibitor by WD40 for a long-lasting instant performance that protects your aluminum for months on end. It works in the same way as a protective spray, but paint cures and obviously changes the color and texture of aluminum.
For vehicles, structures, and other aluminum surfaces that are prone to corrosion, protective paint is an excellent choice to go with. If you ever notice water or moisture on the aluminum surface, wipe it down with a dry rag.
It’s not always practical, but moisture can wreak havoc on aluminum by promoting corrosion and creating calcification. You’ll end up with brittle metal rather than tough, durable aluminum.
Whether you choose to paint it with a protective layer or spray on a new coating, you’ll be able to increase the longevity of all types of metal, not just aluminum. Aluminum is one of the best materials for a variety of applications, but corrosion can make any metal significantly less useful.
The reason that aluminum surfaces start to corrode is that they’re exposed to extremely high or low pH. Pitting turns into bigger holes that give way to lime and calcium.
Again, humidity, pH, temperature, wear and tear, and many other factors determine its longevity. You might need to use an abrasive sponge or cloth to scrub away dense layers of corrosion (calcium can build up quickly).
If you’re dealing with plumbing or sections of aluminum that need to be replaced, then you’ll have to use a saw to remove them. Next, weld new sections in place, ensuring that all holes are sealed and the corroded portions are cleaned or removed.
The signs of corrosion on aluminum include a light gray or white powder along with dullness throughout the affected surface. You also might notice small divots circled by brown rings, which is why many people confuse it with rust.
Humidity, temperature, and pH can impact the presence of corrosion on aluminum. Sorry Mister Stark, but iron is a lousy choice for a suit.
Rusting is a specialized form of corrosion that only iron and steel go through. Rather than flaking though, aluminum oxide just forms a hard, whitish-colored surface skin.
When all the aluminum atoms have bonded with oxygen the oxidation process stops. Scratching this oxide skin exposes bare metal, and the process begins again.
First, if chlorides or sulfides are around they’ll attack the aluminum oxide layer. This is an electrical effect experienced when dissimilar metals are brought close together in a conducting liquid.
This can be a problem in boats where brass fittings are close to or even in contact with aluminum. More generally, 1xxx, 3xxx, 5xxx and 6xxx series alloys offer good corrosion resistance.
If you’re concerned about galvanic corrosion look for paint or powder with high electrical resistance. Anodizing is a kind of surface oxidation that can produce some very attractive finishes.
If taking the coating approach, don’t forget that any damage needs immediate attention. In the movie Tony Stark says he moved on from the original iron suit to one made of a gold-titanium alloy.
As the American Chemical Society point out in this YouTube video, that doesn’t make a lot of sense because gold is really dense. They suggest a better option would be Nitin, an alloy of nickel and titanium.
Rust causes metal to change in color and consistency, making it easy to spot. While the protective aluminum oxide layer is very resistant and can renew itself after sustaining damage, certain factors may cause it to become unstable.
Galvanization occurs when two different types of metals are positioned in a way that forms an electrical circuit. Extreme pH levels may also cause aluminum corrosion, as they have been known to break down the protective coating faster than it can repair itself.
Typically, aluminum falls well in a pH between 4.5 and 8.5, potentially causing an issue in climates with clay soil. While aluminum is a strong and durable metal that is great for all kinds of building and construction projects, you can give it a little extra corrosion-fighting power with the right protection.
View our selection of paints and primers, or give us a call at (813) 241-2801 to learn more about keeping your aluminum shiny and smooth. Aluminum oxide corrosion also looks a lot more like aluminum (dull gray to powdery white), so it isn't as easy to notice as rusted iron.
This expanding and color change can produce large red flakes that we all know as rust. While aluminum doesn't rust, it often becomes dull from corrosion, and is often encrusted with brake dust, calcium, lime, tarnish, grease, oil and hard water stains.
Simply washing it off will not work, you need something stronger and more effective to do the job. We recommend Fritz Aluminum Periclean to remove the surface grime, corrosion and buildup followed by Fritz polish (paste or liquid) to restore a brilliant shine.
Works great on fuel tanks, gas pumps, mag/Alcoa wheels, diamond plate, framing, step plate, engine parts, and more. Corrosion of any metal can significantly impact its functional strength causing structural damage like cracks, partial fracture, and total material failure in extreme cases.
It means that while nascent aluminum will react with oxygen and water in the environment, the resulting compound will form a layer on the surface protecting the material underneath from further corrosion. This non-reactive oxide layer sticks well to the surface and does not flake off easily, similarly to stainless steel.
Understanding these different corrosion phenomena is the first step in applying control measures to reduce or completely prevent their occurrence. These are dry, wet and damp, depending on the moisture levels of the service environment.
As the moisture content can change quite a bit depending on your geographical location, some regions will observe greater corrosion than others. Other environmental factors that affect the extent of atmospheric corrosion are wind direction, temperature and precipitation changes.
Concentration and variety of pollutants in the air, closeness to large water bodies, etc. Creating pockets of water for rain and condensation, for example, are harmful design flaws.
For example, if aluminum and brass are in contact or even close to each other and placed in seawater, a galvanic cell is formed. Pitting corrosion generally occurs in regions where salt is present in the atmosphere, as the presence of chloride anions is responsible for it.
The worst case of pitting corrosion is observed in the presence of alkaline and acidic salts. The existence of surface defects at grain boundaries and second phase particles is a precursor to pitting corrosion.
Overlapping materials or unintentional design mistakes can lead to the formation of crevices. This oxygen reduction makes the crevice acidic in the presence of chlorides which accelerates the rate of corrosion.
When it comes to aluminum, the grain boundary is electrochemical different compared to the alloy microstructure. This causes an electrochemical potential set up between the two and an exchange of electrons takes place.
There are multiple variations of intergranular corrosion based on thermochemical treatments and metallic structures. The 6xxx series alloys, for instance, are relatively less susceptible to this type of aluminum corrosion.
This is predominantly evident in aluminum products that have undergone hot or cold rolling processes. The term exfoliation comes from the fact that the corrosion product is more voluminous and gives the impression of lifting from the material surface.
This type of aluminum corrosion expands above the surface as well as sideways building up stresses in the product. In turn, this causes a wedging action initially at the surface before it migrates into the bulk of the product.
The 2xxx, 5xxx, and 7xxx series are more prone to exfoliation corrosion due to their highly directional grain structures. The susceptibility to exfoliation corrosion can be modified by using heat treatment methods to redistribute the precipitates.
This type of corrosion can happen with products constantly exposed to a highly acidic or alkaline medium. In high and low pH solutions, the oxide layer is also unstable and does not protect the metal underneath.
When this solution comes into contact with an aluminum surface or vessel, it deposits these copper ions onto it. The larger the difference between aluminum and the deposited ion in the galvanic series, the worse the corrosion.
Even a concentration of 1 ppm copper ion solution is known to perform serious corrosion on the aluminum surface. Some important heavy metals are copper, mercury, tin, nickel, and lead.
High yield strength alloys are more likely to suffer from stress corrosion cracking. The existence of carbonate and silica content in water can further augment the corrosion rate.
Improving the water quality means maintaining the pH level as close to neutral as possible (<9), and reducing silica and carbonate content. It is a well-known fact that fatigue can cause complete failure of a product if left unchecked.
In the case of aluminum, fatigue cracks can act as initiation sites for pitting corrosion. Corrosion fatigue in aluminum occurs when it is repeatedly subjected to low stress for long periods of time.
The crack initiation and propagation takes place with greater ease in a corrosive environment like seawater and salt solutions. It also remains largely unaffected by stress direction as the crack propagation is mostly transgranular.
Coliform corrosion occurs and spreads easily in the presence of chloride anions and high humidity. Coliform corrosion can be prevented by keeping the surface free of damage and closing all the small gaps using paint or wax.
Some of these organisms are capable of consuming oil and excreting acids that can cause corrosion of the aluminum vessel used for storing. This acid causes pitting corrosion in the aluminum vessel, eventually leading to leakage.