Corrosion Resistance and Other Advantages of Using Aluminum

There are many reasons to choose aluminum for industry solutions. However, by far the most popular and talked about reason is its natural corrosion resistance. In addition to this natural ability, it is possible to further prevent corrosion through design. This is very beneficial to the long-lasting durability of the finished part or product, especially in industries and situations where corrosion is a concern. The more you explore the advantage of using aluminum in the manufacture of products for your business, the more reasons you will find to keep using aluminum extrusion as an important part of your business model.

Untreated Aluminum
Did you know that aluminum corrosion resistance is excellent even in untreated aluminum? Aluminum works well in most environments. The reason why it has this ability is that it forms a very thin, yet very effective, oxide layer that works to prevent oxidation. This is something that occurs naturally and spontaneously in nature. The oxide layer is impermeable and adheres very strongly to the aluminum alloy. However, even if it were to become damaged mechanically, either through abrasion or by direct cutting, the oxide layer is able to repair itself immediately, to offer continued corrosion resistance protection.

The pH range for untreated aluminum that is stable is typically in the general range of pH 4-9. The most common types of corrosion that can affect metals in most environments include galvanic corrosion, crevice corrosion, and pitting. Crevice corrosion is one of those types of corrosion that can also be overcome in other ways. It is possible to prevent corrosion through design by creating smarter aluminum extrusions that benefit from even more advantages of using aluminum. That, coupled with the natural corrosion resistance, can create a viable solution that will provide long-lasting protection for the finished product.

What is Galvanic Corrosion?
If there is contact between two different types of metals and an electrolytic bridge, galvanic corrosion may occur. The way it works is that the “least noble” metal in the metal combination is what will corrode. This least noble metal becomes the anode and the greatest noble metal becomes the cathode, which immediately becomes further protected against corrosion. Aluminum is typically the least noble metal in most metal combinations, meaning that it will have a greater risk of galvanic corrosion than other metals.

It is important to note that you can still prevent corrosion through design, taking into account the advantages of using aluminum. Galvanic corrosion can only occur when there is contact with a metal that is more noble or if there is an electron conductor that has a higher chemical potential than aluminum, such as graphite. It must also have an electrolyte with good conductivity at work between the two metals. Knowing this, it is possible to prevent corrosion through design or by intent of how the materials will be used.

Risk for galvanic corrosion is reduced when:

  • the materials are stored in a dry, indoor environment
  • the secondary metals are not carbon steel, stainless steel or copper
  • there is no presence of an electrolyte or the electrolyte has poor conductivity
  • the environment has a low chloride level

What is Pitting?
The most common type of corrosion is known as pitting. However, because it can only occur in the presence of an electrolyte, such as water or moisture, that contains dissolved salts, it isn’t always a concern. It is called pitting because the corrosion is revealed in very small pits that can only reach a minimum fraction of the thickness of the metal. It is more of an aesthetic corrosion and the natural corrosion resistance of aluminum provides some protection, it isn’t anything that could threaten the strength or durability of the aluminum part or product. In fact, surface treatments, such as painting, coating, or anodizing, can help counteract pitting completely, and corrosion resistance is boosted further if the surface is cleaned regularly to maintain its appearance.

What is Crevice Corrosion?
While it is not common for extruded profiles to experience crevice corrosion, it can occur in certain industries, especially the marine industry or in areas where the material is exposed regularly to water or heavy moisture. One of the advantages of using aluminum extrusion is the ability to prevent corrosion through design. By eliminating narrow crevices in the profile, water won’t be as likely to collect and cause this type of corrosion over time. Sometimes simply covering the surface with a tarp or other covering can prevent the water or moisture from coming in contact with the part or product to provide additional corrosion resistance.

Design Custom Aluminum Extrusions at Silver City Aluminum
If you are interested in learning more about the advantages of using aluminum in your industry, or if you would like to get a quote on creating custom extrusion profiles that can help you to prevent corrosion through design, give us a call at 508-824-8631. Our team of experienced engineers and technicians can help you take advantage of aluminum’s natural corrosion resistance to prevent crevice, pitting, and galvanic corrosion on your finished product.