Did you know that aluminum alloys are among the most widely used metals in various industries due to their excellent strength-to-weight ratio and resistance to corrosion? When it comes to CNC (Computer Numerical Control) machining, two popular aluminum alloys often come into focus: 6063 and
While their applications are diverse, the differences in their corrosion resistance can significantly impact their use in several environments, especially those exposed to moisture and corrosive elements. In this blog, we will explore the distinctive characteristics of 6063 and 7075 aluminum alloys, their corrosion resistance, and the implications for CNC machining processes.
Understanding Aluminum Alloys
Aluminum alloys can be broadly categorized into two categories: wrought and cast alloys. Both types offer unique properties tailored for specific applications. The 6000 series alloys, like 6063, are particularly known for their good corrosion resistance, excellent extrudability, and moderate strength. The 7000 series alloys, including 7075, are popular for applications requiring high strength. However, with increased strength comes varying levels of corrosion resistance.
Composition of 6063 Aluminum
6063 aluminum is primarily composed of aluminum with magnesium and silicon as its main alloying elements. This combination provides an excellent balance of corrosion resistance, workability, and mechanical properties. The typical composition includes:
7075 aluminum distinguishes itself through its high strength gained from a different alloying approach. Typically, it contains zinc as its major alloying element, along with magnesium and small amounts of copper, which contribute to its strength. The typical composition includes:
Aluminum (Al): 90.7% minimum
Zinc (Zn): 5.1 – 6.1%
Magnesium (Mg): 2.1 – 2.9%
Copper (Cu): 1.2 – 2.0%
Chromium (Cr): 0.18% maximum
Iron (Fe): 0.5% maximum
Silicon (Si): 0.4% maximum
Titanium (Ti): 0.2% maximum
Corrosion Resistance: A Comparative Analysis
Corrosion resistance is a critical factor in selecting aluminum alloys for various applications, particularly in environments where exposure to moisture, salt, and other corrosive elements is a concern. Below, we explore the corrosion resistance of both alloys and the implications for CNC machining.
Corrosion Resistance of 6063 Aluminum
6063 aluminum is known for its excellent corrosion resistance, thanks to its alloying elements and the natural oxide layer that forms on its surface. This oxide layer acts as a protective barrier against environmental corrosives. The key factors include:
Natural Oxide Layer: When exposed to air, 6063 aluminum quickly develops a protective aluminum oxide layer that prevents further oxidation.
Workability and Finish: The alloy’s good workability allows for surface treatments such as anodizing, which can greatly enhance corrosion resistance.
Applications: 6063 is commonly used in architectural applications, window frames, and other products where aesthetics and corrosion resistance are important.
Corrosion Resistance of 7075 Aluminum
In contrast, 7075 aluminum is known for its high strength but relatively lower corrosion resistance. Key considerations include:
Natural Oxidation: While it also develops an oxide layer, this layer is generally less protective than that of
Potential for Pitting: In chloride-rich environments (like marine applications), 7075 can suffer from pitting corrosion, making it less ideal for exposure to seawater or salty conditions.
Surface Treatments: Anodizing and other coatings can improve corrosion performance, although the inherent strength benefits may be offset by the lower resistance.
Comparing Corrosion Resistance in Different Environments
To fully understand the implications of using each alloy, we must examine their performance under diverse environmental conditions:
Marine Environments: For applications like boat parts, 6063 aluminum offers better long-term performance. However, when strength is crucial, 7075 could be used with special coatings to mitigate corrosion risks.
Industrial Settings: In settings that involve exposure to strong chemical agents, 6063 again tends to perform better due to its robust oxide layer.
Outdoor Structures: For architectural elements exposed to weather elements, 6063 aluminum is the preferred choice because it maintains aesthetic value without significant corrosion concerns.
CNC Machining Considerations for 6063 and 7075 Aluminum
CNC machining of these aluminum alloys requires nuanced approaches to fully leverage their distinct properties. Below we outline considerations during the machining process for both alloys.
Machining 6063 Aluminum
Tool Selection
Cutter Materials: Carbide tools are commonly favored, as they offer better wear resistance and can handle the ductility of 6063 effectively.
Cutting Speeds: Recommended cutting speeds range from 250 to 1000 SFPM, depending on the tooling and circumstances.
Surface Treatments
Anodizing: Post-machining anodizing can enhance corrosion resistance and improve appearance.
Post-Processing
Removing Burrs: After machining, burrs need to be removed to maintain both function and aesthetics, often through tumbling or manual deburring techniques.
Machining 7075 Aluminum
Tool Selection
Tooling Material: While carbide tools can be used, high-speed steel may result in quicker wear due to the material’s hardness.
Cutting Speeds: Higher cutting speeds are permissible, typically around 300 to 1200 SFPM, driven by tool material and cooling techniques.
Surface Treatments
Coatings: Applying a suitable coating can improve pitting resistance and overall longevity when exposed to corrosive environments.
Post-Processing
Heat Treatment: Many 7075 parts undergo heat treatment processes post-machining, which undoubtedly can affect corrosion resistance. Proper surfaces should still be protected.
Common CNC Machining Challenges
Both materials exhibit unique challenges during machining:
Chip Control: Effective chip evacuation is critical, especially with 7075 aluminum, to prevent them from bonding or causing damage.
Thermal Management: Utilizing high-performance cutting fluids can reduce machining temperature and improve the part’s surface finish for both alloys.
In conclusion, while both 6063 and 7075 aluminum alloys have their respective places in the world of CNC machining, understanding their corrosion resistance is crucial for making the right material choice. 6063 excels in applications where aesthetics and resistance to environmental factors are a must, while 7075 provides unparalleled strength but requires additional consideration for mitigating corrosion risks.
By understanding these differences, engineers, designers, and manufacturers can choose the appropriate alloy for their specific needs, ensuring suitable performance, extended product life, and reduced maintenance costs. As industries increasingly prioritize sustainability and durability, the choice between 6063 and 7075 encompasses not just performance but the broader implications of material selection in production and environmental impact.
Next time you’re faced with choosing between these two powerful aluminum alloys, remember that the unique properties of each are tailored for different applications. So consider these factors thoughtfully to ensure your CNC machined products not only meet but exceed industry standards and expectations.
