When ordering custom CNC machined aluminum parts, one common question is whether the parts should be anodized or left with a bare machined surface.
Anodizing can improve corrosion resistance, surface appearance, and wear performance. However, it also adds processing steps and may affect dimensions and final cost.
This guide compares anodized and Raw aluminum, explains how the process works, and covers the material considerations you should know before ordering custom CNC parts.
Anodized Aluminum vs. Raw Aluminum: Key Differences
The main difference is that anodized aluminum has an electrochemically formed oxide layer on its surface, while non-anodized aluminum retains its original material surface or machining finish.
| Feature | Anodized Aluminum | Non-Anodized Aluminum |
|---|---|---|
| Corrosion Resistance | Improved protection against corrosion | More exposed to oxidation and environmental corrosion |
| Surface Hardness | Harder oxide surface | Retains the original aluminum surface properties |
| Wear Resistance | Better surface wear resistance, depending on the anodizing type | More susceptible to surface wear |
| Appearance | Can provide consistent finishes and colors | Natural metallic appearance or machined finish |
| Surface Protection | Has an additional oxide layer | No anodized protective layer |
| Dimensions | Coating growth may affect dimensions | No anodizing-related dimensional change |
| Cost | Includes additional finishing costs | Generally lower finishing cost |
Anodizing is often a good choice when parts need better surface protection, a specific appearance, or improved wear resistance.
Raw aluminum may be sufficient when appearance and surface protection are less important, or when the part will receive another finishing treatment.
What Is Anodizing and How Does It Work?
Anodizing is an electrochemical surface treatment that creates a controlled aluminum oxide layer on the surface of aluminum parts.
Unlike paint or plating, the oxide layer is formed from the aluminum itself. This layer becomes part of the surface rather than simply sitting on top of it.
The resulting surface can provide improved corrosion resistance, better wear performance, and options for different colors and appearances.
For CNC machined parts, anodizing is commonly used to protect aluminum components while maintaining a clean, consistent finish.
How the Aluminum Anodizing Process Works
The anodizing process generally involves several steps:
- Surface Preparation: Parts are cleaned to remove machining oil, dirt, and other contaminants. Additional pretreatment may be used depending on the required appearance.
- Anodizing: Aluminum parts are placed in an electrolytic bath, where an electrical current forms an oxide layer on the surface.
- Coloring: If a colored finish is required, dyeing can be carried out after anodizing, depending on the selected process.
- Sealing: The anodized surface is sealed to help close its pores and improve corrosion resistance.
- Final Inspection: Parts are checked for appearance and compliance with the specified requirements.
The final result depends on the aluminum alloy, surface preparation, anodizing type, coating thickness, and process conditions.
At Machmaster, CNC machining and anodizing can be coordinated within our own manufacturing facility, including our in-house anodizing production line. This helps us manage machining and surface finishing as part of the same production process.
Before anodizing, the surfaces of CNC parts can also be brushed, polished, and sandblasted. After anodizing, the surface can achieve a high-quality brushed texture and a matte finish.
What Materials Can Be Anodized?
For Machmaster’s CNC machining and surface finishing services, the main materials to consider are aluminum alloys and titanium alloys. However, their anodizing processes and results are different.
Aluminum Alloys
Aluminum is the primary material used for conventional anodizing.
Common CNC aluminum alloys, such as 5052,6061,6063 and 7075, can be anodized. The final appearance and coating performance may vary depending on the alloy composition and surface condition.
Aluminum anodizing is commonly selected for:
- CNC machined housings and enclosures
- Brackets and mounting components
- Automation equipment parts
- Optical and mechanical components
- Custom aluminum structural parts
If appearance or coating consistency is important, specify the aluminum alloy and anodizing requirements before production.
6061 v 7075 Aluminum Anodizing
Titanium Alloys
Titanium alloys can also undergo anodizing, but titanium anodizing is different from conventional aluminum anodizing.
Titanium anodizing is often used to create oxide layers that produce different colors through optical interference. The resulting colors depend on the oxide layer and process conditions.
It is important to distinguish titanium anodizing from aluminum anodizing. They use different process requirements and should not be treated as interchangeable finishing options.
If your project involves titanium CNC parts, confirm the material grade and required surface result before selecting a finishing process.
When Should You Choose Anodized Aluminum?
Anodizing is not necessary for every aluminum component. The right choice depends on how the part will be used.
Choose anodized aluminum when:
- The part needs improved corrosion resistance.
- You want a black, clear, or other available anodized appearance.
- The surface needs better wear resistance.
- The component will be exposed to normal environmental conditions that may affect bare aluminum.
- You need a consistent surface finish across multiple parts.
Non-anodized aluminum may be suitable when:
- The part is used internally and does not require additional surface protection.
- The machined aluminum appearance is acceptable.
- Tight dimensional requirements make additional coating growth difficult to accommodate.
- The component will receive another suitable surface treatment.
If you are unsure, share the part’s application and drawing with your manufacturer before deciding.
What to Consider Before Ordering Anodized CNC Parts
Before requesting a quote, it helps to define a few details that can affect the final result.
1. Aluminum Alloy
Specify the material grade, such as 6061 or 7075. Different alloys may produce different anodized appearances and results.
2. Anodizing Type and Thickness
Specify whether you need Type II or Type III anodizing, along with the required coating thickness where applicable.
3. Color and Appearance
State whether you need clear, black, or another available color. If appearance is critical, provide a sample or visual reference.
4. Dimensional Tolerances
Anodizing changes the surface dimensions of a part. Important mating surfaces, holes, threads, and precision features should be reviewed before production.
5. Areas That Should Not Be Anodized
If certain surfaces must remain untreated, identify them clearly on the drawing. Masking requirements should be confirmed before production.
Providing these details early helps reduce finishing issues and unnecessary production changes.
CNC Machining and In-House Anodizing at Machmaster
Machmaster provides custom CNC machining and anodizing services from our manufacturing facility in Xiamen, China.
With 20 years of manufacturing experience, 40+ CNC machining machines, and an in-house anodizing production line, we can support aluminum parts from machining through surface finishing.
Our capabilities include:
- Custom CNC milling and turning
- Aluminum parts made to customer drawings
- In-house aluminum anodizing
- Common anodized finishes and colors, subject to process confirmation
- Dimensional and visual inspection
- Assembly and finished-goods packaging when required
We also work with customers on titanium CNC machined parts and can review suitable finishing requirements based on the material and application.
Whether you need prototypes or production quantities, send us your drawings and requirements for a manufacturing review and quote.
Request a Quote for Your CNC Parts
To help us review your project, please provide:
- 2D drawings or 3D CAD files
- Material grade
- Required quantity
- Anodizing type, color, and coating thickness, if specified
- Critical dimensions and tolerances
- Any special surface or masking requirements
Our engineering and sales teams will review your requirements and respond within 24 hours.
Frequently Asked Questions
Is anodized aluminum better than non-anodized aluminum?
It depends on the application. Anodized aluminum offers improved corrosion resistance, surface hardness, and appearance options. Non-anodized aluminum may be suitable when additional surface protection is not necessary.
Does anodizing make aluminum stronger?
Anodizing mainly improves surface properties. It does not significantly increase the bulk strength of the aluminum part.
Does anodizing change the dimensions of CNC parts?
Yes. The oxide layer grows from the aluminum surface, so anodizing can affect final dimensions. Critical dimensions and mating features should be considered during CNC machining and finishing.
Can 6061 and 7075 aluminum be anodized?
Yes. Both 6061 and 7075 aluminum alloys can be anodized. However, their final appearance and coating results may differ because of their alloy compositions.
Can titanium alloys be anodized?
Yes. Titanium alloys can be anodized using a process different from conventional aluminum anodizing. The resulting colors and surface properties depend on the titanium grade and process conditions.
Does every aluminum CNC part need anodizing?
No. The decision depends on the part’s operating environment, appearance requirements, corrosion protection needs, and dimensional tolerances. Some parts can be used with their machined surface without anodizing.
