Why 7075 Aluminum CNC Machined Parts Tend to Oxidize

7075 aluminum alloy is known for its high strength and is often used in precision CNC machining applications. However, it is also prone to oxidation during the machining process, which can present some challenges. Here's a closer look at why 7075 aluminum tends to oxidize easily and how to manage it:

Why 7075 Aluminum CNC Machined Parts Tend to Oxidize

Chemical Composition: 7075 aluminum alloy contains elements like magnesium and zinc, which can react with oxygen in the air, leading to oxidation.

Heat Generation: The CNC machining process generates heat, especially during operations like milling or drilling. This heat can accelerate the oxidation process by breaking down the natural protective oxide layer on the aluminum surface.

Removal of Protective Oxide Layer: The natural oxide layer on aluminum provides some protection against further oxidation. However, during CNC machining, this layer can be removed, exposing the underlying aluminum to oxygen and promoting further oxidation.

Surface Finishing Challenges: Once the surface has begun to oxidize, it can be difficult to achieve a clean, uniform finish. The oxidized layer can lead to uneven coloring, white spots, or a rough texture.

Managing Oxidation in 7075 Aluminum CNC Machining

Coolant Use: Applying coolants during the machining process can help to dissipate heat and reduce the rate of oxidation.

Minimize Heat: Using the correct cutting parameters, such as feed rates and cutting speeds, can minimize heat generation and thus reduce the risk of oxidation.

Protective Atmosphere: Machining in a controlled atmosphere or using an inert gas can slow down the oxidation process.

Surface Treatment: Applying a protective coating or anodizing the aluminum after machining can help to restore the protective oxide layer and prevent further oxidation.

Proper Anodizing Process: When anodizing, it's important to control the current carefully. Too high can cause burning, while too low may not produce the desired effect. The anodizing process should be closely monitored to achieve the right film thickness and color.

Material Handling: Avoid frequent exposure to air once the machining process begins, as this can accelerate oxidation.

Post-Machining Cleaning: Cleaning the parts immediately after machining can help to remove any oxidation that has occurred and prepare the surface for further treatment or coating.

Storage Conditions: Store machined parts in a dry and cool environment to minimize the potential for oxidation.

Conclusion

While 7075 aluminum alloy is an excellent material for precision CNC machining due to its high strength-to-weight ratio and workability, its susceptibility to oxidation requires careful management. By taking appropriate measures to control the machining environment, heat, and post-machining treatment, the oxidization issues can be mitigated, ensuring the production of high-quality parts with the desired properties and finish.