Protecting aluminum from corrosion primarily involves applying surface treatments that create a barrier layer.
Aluminum's natural resistance to corrosion comes from a thin, passive oxide layer that forms on its surface. However, this layer can be vulnerable to specific types of corrosion, such as pitting attack, especially in certain environments. To enhance protection, particularly against pitting attack, applying a coating is a highly effective strategy.
Key Protection Methods
According to the reference, protecting aluminum from corrosion, specifically pitting attack, is achieved by applying a coating to the surface. Several common methods achieve this:
Surface Treatments Forming a Coating
Any surface treatment that forms a coating on the aluminum surface will protect it from pitting attack. These coatings act as a barrier, preventing corrosive elements from reaching the underlying metal.
- Painting: Applying paint creates a protective film that isolates the aluminum from moisture and corrosive substances. Paint systems often involve multiple layers, including primers and topcoats, for enhanced durability and protection.
- Anodizing: This electrochemical process thickens the naturally occurring oxide layer on the aluminum surface. The resulting anodic coating is much harder, thicker, and more resistant to corrosion and abrasion than the natural oxide layer.
- Other Surface Treatments: Various other chemical or physical treatments can apply a protective coating, such as powder coating, electroplating with other metals, or applying conversion coatings (like chromate or phosphate coatings) before painting or other finishes.
Preserving the Aluminum Look
Sometimes, the aesthetic appearance of the aluminum surface is important. In such cases, the protective treatment needs to be clear or minimally alter the metal's look.
- Clear Coat: Applying a clear, transparent coating can provide a barrier against corrosion while allowing the natural look of the aluminum to show through. This is similar to painting but uses a clear protective layer.
- Thin Anodic Coating: Anodizing can be controlled to produce a very thin coating that is less opaque than standard anodized finishes. A thin anodic coating is a suitable surface treatment when you want to preserve the aluminum look and still have a surface resistant to pitting.
Summary of Protection Methods
Here's a quick look at common methods based on forming a protective coating:
| Method | Description | Primary Benefit | Appearance Impact |
|---|---|---|---|
| Painting | Applying liquid or powder coatings. | Forms a barrier, offers color/aesthetic options. | Covers the aluminum surface. |
| Anodizing | Electrochemical process to thicken the oxide layer. | Forms a hard, durable, corrosion-resistant layer. | Can be clear, colored, or opaque. |
| Clear Coating | Applying a transparent protective film. | Protects while preserving the natural look. | Minimal impact on appearance. |
| Thin Anodizing | Anodizing with controlled thickness. | Provides pitting resistance, preserves natural look. | Minimal impact on appearance (clear). |
| Other Treatments | Conversion coatings, plating, etc. | Varies depending on treatment; often base for paint. | Varies. |
Ultimately, the best method depends on the specific application, environmental conditions, required lifespan, and desired appearance of the aluminum product. The key takeaway, as highlighted by the reference, is that creating a coating on the aluminum surface is fundamental to protecting it, particularly from pitting attack.
