Metals are processed from ore, and most of them naturally want to corrode back to some form of ore. Gold is one notable exception, as it resists corrosion. This tendency to revert to a more stable, oxidized state is why corrosion is such a common issue with metals. In this blog, we’ll explore aluminum corrosion specifically—how it differs from other types of metal corrosion, the conditions that accelerate it, and effective strategies to prevent it. Whether you’re working with aluminum in construction, manufacturing, or everyday applications, understanding how to protect it is crucial to maintaining its integrity.
Understanding the Differences: Rust vs. Corrosion
Are Rust and Corrosion the Same Thing? Many people often confuse rust with corrosion, thinking they
are interchangeable terms. However, they are not the same. Corrosion is a broad term that refers to the oxidation of metals, where metal atoms combine with oxygen, leading to a gradual or sometimes rapid breakdown.
Rust is a specific type of corrosion that affects only iron and steel. When iron oxidizes, it forms rust, which flakes off and exposes fresh metal underneath. This newly exposed metal then oxidizes, repeating the cycle. Rust formation is accelerated by moisture, which is why it’s such a common issue in damp environments.
Aluminum vs. Steel: How Oxidation Differs
When it comes to oxidation, aluminum behaves differently from steel. Aluminum has a stronger affinity for oxygen, meaning it oxidizes more quickly. However, unlike steel, aluminum oxidation creates a hard, whitish-colored surface layer. This layer, made of aluminum oxide, protects the underlying metal by preventing further oxidation once all aluminum atoms on the surface have bonded with oxygen.
Aluminum Corrosion: What You Need to Know
Aluminum corrosion occurs when this protective oxide layer is compromised. Scratching the surface exposes the bare metal, allowing the oxidation process to start anew. While aluminum corrosion generally doesn’t eat away at the metal, there are two exceptions:
- Presence of Chlorides or Sulfides: These compounds, commonly found in salt water and polluted air, can attack the aluminum oxide layer, leading to corrosion.
- Galvanic Corrosion: This occurs when dissimilar metals, such as brass and aluminum, are in close proximity in a conductive liquid. It’s a common problem on boats where brass fittings might come into contact with aluminum fuel tanks.
How to Prevent Aluminum Corrosion
While you can’t stop aluminum from oxidizing, you can prevent corrosion by taking a few precautions:
Protective Coatings:
- Paint or Other Coatings: These can provide a barrier between the metal and the environment.
- Powder Coating: Offers a durable finish that can help protect aluminum surfaces.
- Anodizing: A surface oxidation process that not only protects but can also create attractive finishes. However, it’s not usually practical for large surfaces.
If you’re concerned about galvanic corrosion, choose a coating with high electrical resistance. Remember, any damage to the coating should be addressed immediately to prevent corrosion from starting.
HinderRUST: Your Solution to Aluminum Corrosion
HinderRUST, formulated with Fluoramics’ Tufoil Technology, is a powerful coating that prevents corrosion by
forming a barrier between metal, moisture, and oxygen. Without moisture or oxygen reaching the metal surface, oxidation cannot occur. Unlike solvent-based products that evaporate quickly, HinderRUST stays on the surface, offering long-lasting protection.
In a B117 salt-fog test conducted by Fluoramics, aluminum treated with HinderRUST demonstrated significantly better resistance to rust and corrosion than untreated areas, particularly in air conditioning cooling coils.
HinderRUST doesn’t just protect aluminum; it safeguards all types of metals. This makes it an ideal choice for protecting HVAC systems, including aluminum fins and cooling coils, as well as metal frames, fan blades, wiring, and copper piping.
Preventing Galvanic Corrosion: Tips and Tricks
To minimize the risk of galvanic corrosion:
- Keep Aluminum Dry: The galvanic effect requires an electrically-conductive liquid, so keeping the aluminum dry is the best preventive measure.
- Use Electrically Insulating Coatings: These can prevent the galvanic effect between dissimilar metals.
- Select the Right Aluminum Grade: Some grades, like 5052 and 3003, offer better corrosion resistance. More generally, 1xxx, 3xxx, 5xxx and 6xxx series alloys offer good corrosion resistance.
- Consider Sacrificial Anodes: Zinc anodes corrode faster than aluminum, sacrificing themselves to protect the aluminum. Though these anodes need periodic replacement, they are a reliable solution.
By understanding the differences between rust and corrosion, and by taking proactive steps to protect your metals, you can extend the life of your equipment and structures, ensuring they stay in top condition for years to come.
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