What You Should Know About Anodizing Aluminum

When using metal components or creating products made from metal, anodizing can be a valuable step in the process, especially with a softer metal like aluminum. The process of anodizing aluminum prevents corrosion, resists scratching, improves aesthetics and creates a more durable product. The following information will help you see the value in completing this process for your metal components.

How Does It Work?

Before anodizing aluminum, the metal is first cleaned to remove any debris on the surface. It is then placed in an electrolytic solution and a positive electric charge is administered directly to the aluminum while a negative charge is sent to plates suspended in the solution. Negative ions are then pulled toward the aluminum.

What Is the Barrier Layer?

During the process in the electrolytic solution, pores on the aluminum open up to let the positive ions out, creating a geometric pattern that erodes into a substrate. The surface of the aluminum bonds with O2 to create aluminum oxide, creating a barrier that protects against corrosion and other chemical reactions. The longer the process continues, the pores extend deeper into the aluminum. Non-hard anodized coatings typically measure about 10 microns. Once the desired depth is reached, a cold water rinse stops the process.

Hard Anodizing

If you need greater corrosion protection for your aluminum, hard anodizing is the right solution. To achieve hard anodizing, a longer barrier process is necessary, often reaching depths of 25 microns or more. While this process takes more time and can be more costly, it provides enhanced durability to the metal.

Is Corrosion Protection Necessary?

Aluminum doesn’t rust, so you may wonder if corrosion resistance is even necessary. The answer is yes. While it can’t rust, aluminum can experience oxidation when exposed to the air. This oxidation is relatively harmless to aluminum, but that’s only when you consider exposure to pure air and water. In the real world, aluminum may be exposed to salt water, acid rain and other contaminants that can have a negative impact on the metal, making corrosion protection a necessity to avoid discoloration or mechanical failure.

Adding Color to Anodized Aluminum

When most people think of anodized aluminum, they think of coloring, which is a common use for the process. Once you have created the pores with the anodizing process, it’s the perfect time to add color to the metal before sealing off the pores with a water rinse. Adding color to aluminum using this process ensures long-lasting color. Because it lies deep within the metal, it won’t scratch off the surface.

Creating the Popular Metallic Look

When you think of something metal, you often think of something shiny. This is the result of the anodizing process. Anodizing is a form of etching that leaves the surface of the metal with a rough texture. Deeper pores mean a rougher texture. The way the light bounces off this surface creates the tell-tale metallic sheen most people recognize.

Use Caution with Your Design

When creating your anodizing bath, it’s important to remember it’s impossible to fully anodize an entire part. After all, the metal must be submerged, yet suspended in the bath, requiring a holder of some form. Any part of the metal concealed by the holder won’t be anodized, so it’s important to position your parts carefully and minimize obstructed areas as much as possible.