How to Prevent Aluminum Corrosion?

Aluminum corrosion is a major concern for industries that rely on aluminum for manufacturing and production. It affects product durability and performance. Understanding how to prevent it is crucial for maintaining the longevity of aluminum structures and components.

What Can Cause Aluminum to Corrode?

How Environmental Conditions Impact Aluminum Corrosion

Environmental factors play a significant role in the corrosion of aluminum. Understanding how these factors interact with aluminum helps in developing effective strategies to combat corrosion. Below is a detailed analysis of how specific environmental elements contribute to corrosion:

1. Humidity and Moisture

High humidity levels or exposure to moisture are among the most significant contributors to aluminum corrosion. When moisture comes into contact with aluminum, it reacts with the metal's surface, creating a thin oxide layer. However, in extreme cases, this oxide layer may not be enough to prevent further corrosion, especially when moisture accumulates in small cracks or crevices.

2. Salty Air and Marine Environments

Aluminum corrosion is particularly problematic in coastal or marine environments due to the presence of salty air. Salt (sodium chloride) accelerates the breakdown of aluminum by forming chloride ions, which attack the protective oxide layer and leave the metal exposed. Aluminum exposed to marine air can lose up to 10 times its protective oxide layer in just one year, significantly reducing its durability. As a result, aluminum products used in marine environments require more rigorous protection against corrosion, such as the use of sacrificial coatings or anodization.

3. Industrial Chemicals and Pollutants

Industrial environments often expose aluminum to corrosive chemicals, such as acids, bases, or other pollutants. According to the study that the corrosion rates average 0.8–0.28 µm/year (0.03–0.11 mils/year). These chemicals can weaken or destroy the oxide layer, making aluminum susceptible to pitting or more severe forms of corrosion.

4. Compromised Surfaces and High Temperature

While aluminum is naturally resistant to corrosion, any physical damage to its surface can expose the metal beneath to the elements, significantly speeding up the corrosion process. Scratches, dents, and cracks can compromise the integrity of the oxide layer, leaving the underlying aluminum vulnerable to further damage. In these cases, the corrosion can spread quickly, particularly in areas where moisture or pollutants can settle.

According to a study "Corrosion of aluminum alloys in high-temperature water", it shows that aluminium alloys can be attacked in three ways in high-temperature water: by grain boundary attack, by accelerated attack and by uniform attack. For example, at 230° C in flowing water a corrosion rate of 0.1 mm/year is observed. This is increased to about 0.3 mm/year under boiling at 70 watt/cm2.

[1] Knowing what causes aluminum profile to become brittle

Five Common Corrosion Types of Industrial Aluminum

Corrosion is a significant concern in aluminum components, especially in industrial applications where exposure to various environmental factors is inevitable. Below are five of the most common types of corrosion affecting aluminum[1], with an in-depth look at their causes, impacts, and prevention strategies:

1. Pitting Corrosion

Pitting corrosion is a localized form of corrosion that forms small pits, dots, or holes on the aluminum surface. Unlike uniform corrosion, which affects the entire surface, pitting creates discrete points of weakness that can lead to significant degradation if left unchecked. It is typically seen in aluminum exposed to atmospheric conditions, freshwater, or neutral aqueous solutions.

Key Features of Pitting Corrosion:

• Localized holes or pits on the surface.
• Common in marine or chemical environments.
• Can lead to perforation if not addressed.
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2. Galvanic Corrosion

Galvanic corrosion, also known as bimetallic corrosion, occurs when aluminum comes into contact with a more noble metal and exposes in the electrolyte solution such as salt water, acid, then forming a galvanic cell. Aluminum's negative electrochemical potential makes it prone to corrosion in these situations, as it becomes the anode in the galvanic cell and accelerates its own corrosion.

Key Features of Galvanic Corrosion:

• Occurs when aluminum contacts dissimilar metals.
• The aluminum acts as the anode, accelerating its corrosion.
• The severity depends on the difference in electrochemical potentials.
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3. Crevice Corrosion

Crevice corrosion happens in tight spaces where moisture, salt, or chemicals can accumulate, leading to corrosion in areas that are otherwise protected. Even highly corrosion-resistant alloys can suffer from crevice corrosion, making it a unique challenge in aluminum corrosion prevention.

Key Features of Crevice Corrosion：

Happens in confined areas where moisture, salt, or chemicals can accumulate, often where protection is otherwise present.

Even highly corrosion-resistant alloys, including aluminum, can be vulnerable to crevice corrosion.

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4. Intercrystalline Corrosion

Intercrystalline corrosion, or intergranular corrosion, occurs along the grain boundaries of aluminum alloys. This form of corrosion is typically linked to poor heat treatment or alloying elements that precipitate out along the grain boundary, creating weak spots that accelerate the corrosion process.

Key Features of Intercrystalline Corrosion:

• Occurs along grain boundaries in aluminum alloys.
• Caused by improper heat treatment or alloy composition.
• Leads to the weakening of the material structure.
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5. Filiform Corrosion

Filiform corrosion is a type of subfilm corrosion that develops under protective coatings like paint or anodized films. It appears as worm-like or thread-like patterns that spread beneath the protective layer, causing damage to the underlying aluminum surface. Unlike other forms of corrosion, filiform corrosion is generally seen beneath non-anodized coatings.

Key Features of Filiform Corrosion:

• Occurs under coatings like paint or anodized layers.
• Appears as worm-like or thread-like patterns.
• Typically found under non-anodized or improperly applied coatings.
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How to Prevent Aluminum Corrosion

Preventing corrosion in aluminum is a critical step to ensure the longevity, strength, and functionality of aluminum components, especially in industrial applications where exposure to harsh environmental factors is inevitable. Choosing the right aluminum material and surface finishing are all beneficial for your equipment. Here are some detailed methods for preventing aluminum corrosion, supported by research and real-world data.

1. Use of Protective Coatings

Applying a protective coating to aluminum surfaces is one of the most effective methods to prevent corrosion. Coatings such as anodizing or powder coating provide a physical barrier that prevents direct contact with moisture, chemicals, and other corrosive agents. Anodizing, in particular, not only protects aluminum but also enhances its natural corrosion resistance by thickening its oxide layer.

• Anodizing: The anodizing process increases the thickness of the natural oxide layer on aluminum, making it more resistant to corrosion. Using anodizing can increase the aluminum's resistance to corrosion by up to 50 times compared to untreated aluminum. The oxide layer created through anodizing is typically around 10 to 15 μm, but in some industrial applications, the thickness can be increased to as much as 30 μm by Kaixin Aluminum manufacturing. This layer is durable and offers resistance to many environmental factors, including water, salt, and acidic conditions.

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• Powder Coating: Powder coating provides a durable, aesthetically pleasing finish to aluminum products, which is particularly useful for outdoor and exposed applications. It creates a non-porous layer that can withstand harsher environments, including saltwater, UV light, and extreme temperatures. And powder-coated aluminum surfaces are up to 4 times more resistant to corrosion compared to uncoated aluminum alloy.

2. Use of Corrosion-Resistant Aluminum Alloys

Some aluminum alloys are naturally more resistant to corrosion than others. When selecting aluminum for specific applications, choosing the appropriate aluminum alloy based on its environmental exposure is essential for equipment operation. Alloys such as 5xxx and 6xxx series have higher resistance to corrosion, particularly in high-consumption devices.

5xxx Series: These alloys, such as 5052, are highly resistant to corrosion in saltwater environments, making them ideal for marine applications. They contain a higher percentage of magnesium (3-5%), which enhances their resistance to pitting and galvanic corrosion.

6xxx Series: Alloys like 6061 are popular for structural applications and have good corrosion resistance, especially in atmospheric conditions. However, they are less resistant to saltwater exposure compared to 5xxx alloys. Adding a protective coating can further im

3. Regular Cleaning and Maintenance

Regular cleaning and maintenance of aluminum surfaces are essential to prevent the buildup of corrosive substances that can promote corrosion. Dirt, salt, and other pollutants can accumulate on aluminum surfaces and initiate corrosion if left untreated. The cleaning process should be done using non-corrosive solutions to avoid damage to the metal.

• Cleaning Frequency: Aluminum components in marine environments should be cleaned every 1-2 months to prevent the buildup of salt and other corrosive agents. In industrial environments, cleaning may need to be done more frequently, especially in areas exposed to chemicals or heavy pollution.

• Maintenance Tips: Using soft cloths or brushes during cleaning is crucial to avoid scratching the aluminum surface. It's recommended to use mild detergents and water or a specially designed aluminum cleaner to ensure that no harmful chemicals are used that might damage the surface.

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4. Environmental Control

Controlling the environmental conditions in which aluminum components are stored or used can significantly reduce the risk of corrosion. Reducing exposure to moisture, extreme temperatures, and harsh chemicals prevents corrosion from forming in the first place.

• Humidity and Moisture Control: High humidity and moisture are significant factors that contribute to aluminum corrosion, especially in industrial environments. The study on "Research reveals how humidity affects atmospheric corrosion of aluminum metal" states how the humidity accerlates the rate of aluminum corrosion. When there is enough water vapor in the air, it forms a thin water film on the surface of aluminum that varies with the humidity in the air, acting like a "catalyst" to accelerate aluminum corrosion. However, proper ventilation, dehumidifiers, and climate-controlled storage can mitigate this risk.

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• Temperature Fluctuations: Extreme temperature changes in aluminum can lead to the expansion and contraction of aluminum, which may weaken protective coatings and increase corrosion susceptibility. By stabilizing temperatures in storage or usage areas, the risk of temperature-induced corrosion can be reduced.

• Chemical Exposure: Exposure to harsh chemicals, such as sulfuric acid or chlorine, can rapidly degrade aluminum. Using protective covers, coatings, or barriers can help shield aluminum components from these corrosive agents.

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Conclusion

Aluminum corrosion can be a serious issue in many industrial applications, but with the proper prevention methods in place, it can be significantly reduced.

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