What Is the Best Aluminum to Anodize for Enhanced Durability?

Aluminum is a widely used material in various manufacturing industries. It is lightweight, affordable, and corrosion-resistant. Aluminum is not always used in its unfinished form. You have to convert the metal surface into a durable finish through the anodizing process. However, not all aluminum is created equally when it comes to anodizing. The effectiveness of the anodizing process varies based on the aluminum’s chemical composition. This affects factors like surface hardness, aesthetics, and overall longevity. Hence, it is important to carefully select the right aluminum alloy to achieve the best result. 

This article explains what aluminum anodizing is, the best types of aluminum alloys suitable for anodizing, and tips for maintaining the finish of anodized aluminum products. 

What is Anodizing, and Why is it Important for Aluminum

Anodizing is an electrolytic passivation process that enhances the surface properties of metals, particularly aluminum. It converts the metal surface into a thick protective oxide layer that serves both functional and decorative purposes. Unlike other surface finishing techniques, anodizing is more durable. Rather than sitting on the metal top, the anodized layer is a part of the surface itself. This extra is harder and highly resistant to corrosion when compared to raw aluminum. 

Furthermore, the process of anodizing begins with cleaning and pre-treatment to ensure a uniform finish. You then submerge the aluminum into a prepared electrolyte bath, usually sulfuric or chromic acid. When an electric current is passed through, aluminum atoms at the surface react with oxygen in the electrolyte to form an aluminum oxide layer. This porous oxide layer is then sealed using appropriate techniques. Anodized aluminum is durable and wear-resistant. Additionally, it does not chip or peel easily when used for a prolonged period. 

Types of Aluminum Best Suited for the Anodizing Process

There are various grades of aluminum available. However, not all are amenable to the anodizing process. The following are common aluminum alloys you can finish using anodizing. 

• 7XXX Series

This is a common grade of aluminum alloy that you can anodize with ease. The primary alloying elements are zinc, magnesium, copper, and chromium. This aluminum type is known for its high strength and good fatigue resistance. Hence, you will find it in high-stress applications like aerospace and military. However, the high copper content in some alloys like 7075 can cause discoloration when subjected to the anodizing process. You should stick to grades like 7050 with less copper. This grade is better suited for functional anodizing. 

• 6XXX Series

It is unarguable that this series is the most common when it comes to aluminum anodizing. The 6XXX series contains mainly magnesium and silicon alongside aluminum metal. The excellent anodizing properties of this grade can be attributed to the low copper content. Additionally, the presence of magnesium and silicon provides a clean and uniform anodized layer. Common alloys for anodizing are 6061, 6063, and 6082. They are suitable for both decorative and functional anodizing. Additionally, you can dye them to a wide range of colors. 

• 5XXX Series

You can also refer to this series as aluminum-magnesium alloys. This aluminum grade is known for its high corrosion resistance. Hence, they perform well in marine and coastal environments. Additionally, the 5XXX series has good weldability and moderate strength. The best alloys in this series for anodizing are 5005, 5052, and 5083. They are easy to handle. Note that alloys with high magnesium content pose some anodizing challenges. They are not ideal for decorative anodizing because of the grayish and dull finishes produced. 

• 4XXX Series

Another aluminum grade you should consider anodizing is the 4XXX series. The major alloying element here is silicon. Part manufacturers use this grade extensively because of its good corrosion resistance and low expansion properties. Hence, you will find it in high-wear applications like engine parts and military components. Note that some silicon alloys do not anodize well. This is because silicon reacts when anodized to produce a dark and mottled finish. While this may not affect the functionality of the part, it is not aesthetically pleasing.

• 3XXX Series

It is not uncommon to anodize this grade of aluminum during part manufacturing and finishing. The high manganese content provides good corrosion resistance and moderate strength. Of the types of aluminum alloys available, 3003 and 3105 are the most suitable for the anodizing process. You use them in applications where appearance is less critical. The reasons behind this are not far-fetched. Compared to other series like 6XXX, the anodizing results in a dull appearance. 

Applications Where Anodized Aluminum is Highly Effective

Anodized aluminum is indispensable in modern manufacturing industries because of its enhanced aesthetics and superior corrosion resistance. The products are durable and can stand the test of time. Below is an extensive discussion of applications that cannot do without anodized aluminum. 

• Architecture and Construction

The use of anodized aluminum in architecture and construction applications is nothing new because of its exceptional durability and aesthetic versatility. Most architectural structures are used outdoors where unfinished aluminum parts may not be effective. The anodizing process protects building facades and cladding from corrosion and environmental factors. You can also use it for window frames, doors, railing, and fencing.

• Automotive and Transportation 

Automotive part manufacturers use anodized aluminum extensively for its functional and decorative advantages. The high strength-to-weight ratio also provides additional benefits. Anodized aluminum car components save costs and improve overall fuel efficiency. Key applications of anodizing in automotive and transportation include exterior body panels, trim, wheels, rims, and aircraft fuselage. 

• Electrical and Electronics 

Another industry that relies heavily on anodized aluminum is electrical and electronics. The parts resist corrosion and ensure proper dissipation of heat. Furthermore, the anodizing process enhances conductivity when used in electrical connectors. Using anodized aluminum for heat sinks, electronic enclosures, panels, and cabinets improves appearance and enhances their lifespan. 

• Consumer Goods and Household Items

Anodized aluminum is a popular choice for consumer goods and household items including cookware, home appliances, and sports equipment. Anodizing is the method used when finishing these components because of durability and aesthetic flexibility. Using anodized aluminum for pots, baking trays, and pans enhances the cooking experience. They offer superior non-stick properties and are more resistant to scratching. 

• Marine Applications

Anodized aluminum thrives in marine and coastal applications. The saltwater environment is unfavorable to unanodized aluminum components as they degrade because of the harsh conditions. The presence of an anodized layer protects these structures and reinforces their strength. They maintain a clean and polished appearance in harsh marine environments. Key applications of anodized aluminum in the marine industry include boat hulls, decks, railings, and dock equipment. 

• Decorative and Artistic Applications 

Anodizing is usually the preferred surface finishing method for decorative and artistic applications. Before sealing, you can apply different custom colors that enhance the visual appeal of a product.  This makes it ideal when fabricating sculptures and art installations that have an attractive and eye-catching look. Other applications include jewelry, fashion accessories, awards and trophies. 

Tips for Maintaining the Finish of Anodized Aluminum Products

Like other materials, you have to properly maintain anodized aluminum parts for them to continue performing optimally. Let’s look at common tips for maintaining the finish of anodized aluminum products.

• Regular Cleaning 

You must routinely clean anodized aluminum components at least every 3 to 6 months when using them. Contaminants including dirt and grease can accumulate on their surface which dulls the shine over time. When cleaning, it is important to use mild detergents and soft cloth to avoid compromising the surface integrity. Make sure you rinse thoroughly to remove soap residue. 

• Protection 

While the anodizing process provides superior protection against corrosion, you should consider adding extra protection to prolong the material’s life and maintain its attractive finish. This will help shield from ultraviolet radiation that can cause the anodized layer to fade or become discolored. Additionally, avoid exposing anodized aluminum parts deliberately to harsh chemicals like strong acids of alkaline solutions.

• Storage and Handling

You have to properly store and handle anodized aluminum products when not in use to prevent scratches and physical damage. Always store in a clean, dry place away from any corrosive substances and moisture. When storing, use soft padding and cloth wraps to avoid direct contact with hard surfaces. Furthermore, use protective packaging during transport so there will not be any form of damage or abrasion.

• Inspection and Maintenance 

Regular insertion and maintenance make all the difference when using anodized aluminum components. This will ensure it retains its appearance and continues to function as expected. Visually inspect for damage and check for pitting around areas exposed to moisture and chemicals. If necessary, reapply protective coatings to restore the surface’s protection. 

Conclusion

Using the right aluminum during anodizing determines how the process will go and the result. It is crucial for achieving enhanced durability and performance. The top alloys for anodizing are 6061, 6063, and 7075 because of their ability to develop strong, protective layers. This makes them ideal for demanding applications like architecture, marine, and automotive. Do you have further questions and clarifications? Reach out to Zintilon today for all your manufacturing needs.