Yes, aluminum is a metal. More specifically, it is a lightweight, silvery, non-ferrous metal known for its low density, corrosion resistance, electrical conductivity, thermal conductivity, and strong usefulness in manufacturing. If you see the spelling aluminium, it refers to the same element. Aluminum is the common American spelling, while aluminium is common in British English and many international markets.
That quick answer is useful, but buyers and engineers usually need more than a dictionary definition. The practical question is not only whether aluminum is a metal, but why it behaves differently from steel, copper, titanium, or plastic, and why it is so widely used in CNC machined parts. This guide explains aluminum as a metal from a material selection and manufacturing perspective, with clear comparisons, alloy examples, CNC machining notes, finishing options, and design guidance.
For custom aluminum components, MTSPi supports aluminum CNC machining, CNC milling, finishing, and inspection for prototypes and production parts.
Is Aluminum a Metal?
Aluminum is a metal because it has the core characteristics associated with metallic elements: metallic bonding, good electrical and thermal conductivity, ductility, malleability, a metallic luster, and the ability to form useful alloys. On the periodic table, aluminum has the symbol Al and atomic number 13. It belongs to the boron group, but in practical engineering it is treated as one of the most important commercial metals.
Unlike iron and steel, aluminum is a non-ferrous metal. That means it does not use iron as its main base element. This distinction matters because non-ferrous metals generally behave differently in weight, corrosion resistance, magnetism, conductivity, and machining. Aluminum is also not magnetic under normal conditions, which makes it useful in electronic housings, instrument components, aircraft parts, and fixtures where magnetic interference must be avoided.
Aluminum vs Aluminium: Are They the Same?
Yes. Aluminum and aluminium mean the same material. The spelling difference is regional, not technical. In the United States and Canada, aluminum is the dominant spelling. In the United Kingdom, Europe, and many other markets, aluminium is more common. A drawing, RFQ, or datasheet using either spelling can refer to the same metal.
For international sourcing, the alloy designation matters more than the spelling. A request for aluminum 6061-T6 or aluminium 6061-T6 is much clearer than simply asking for aluminum. The grade, temper, surface finish, tolerance, and inspection requirements define the real manufacturing result.
Key Properties of Aluminum
| Property |
Why It Matters in Real Parts |
Manufacturing Note |
| Low density |
Aluminum is much lighter than steel, which helps reduce part weight. |
Useful for aerospace, robotics, fixtures, handheld products, and moving assemblies. |
| Corrosion resistance |
A natural oxide layer helps protect the surface from many environments. |
Anodizing or coating can improve protection and appearance. |
| Good machinability |
Many aluminum alloys cut efficiently and hold fine details. |
Sharp tools, chip evacuation, and proper feeds help maintain finish and accuracy. |
| Thermal conductivity |
Aluminum transfers heat well. |
Useful for heat sinks, housings, brackets, and thermal management parts. |
| Electrical conductivity |
Aluminum conducts electricity, though not as well as copper. |
Useful in electrical housings, bus bars, connectors, and lightweight conductive components. |
| Ductility |
Aluminum can deform before fracture and can be extruded, rolled, bent, or machined. |
Formability depends heavily on alloy and temper. |
| Surface finish compatibility |
Aluminum accepts anodizing, bead blasting, polishing, plating, and coating. |
Finish requirements should be specified before quoting. |
Is Aluminum a Pure Metal or an Alloy?
Pure aluminum exists as an element, but most industrial aluminum parts are not made from commercially pure aluminum. They are usually made from aluminum alloys. An alloy is a metal mixture designed to improve strength, hardness, machinability, heat treatment response, corrosion behavior, or formability.
Common alloying elements include magnesium, silicon, copper, zinc, manganese, and chromium. These small additions can change performance dramatically. For example, 6061 aluminum is valued for balanced machinability, corrosion resistance, and weldability, while 7075 aluminum is selected when higher strength is needed.
Common Aluminum Alloy Families
| Series |
Main Alloying Element |
Typical Strengths |
Common Uses |
| 1000 series |
Mostly pure aluminum |
Excellent conductivity and corrosion resistance, low strength |
Electrical, chemical, reflective, and formed parts |
| 2000 series |
Copper |
High strength and good fatigue performance |
Aerospace and structural parts where corrosion protection is managed |
| 3000 series |
Manganese |
Good formability and corrosion resistance |
Sheet metal, housings, tanks, and general formed products |
| 5000 series |
Magnesium |
Good corrosion resistance, especially marine environments |
Marine, automotive, welded structures, and sheet applications |
| 6000 series |
Magnesium and silicon |
Balanced strength, machinability, corrosion resistance, and anodizing response |
CNC machined parts, frames, brackets, fixtures, housings |
| 7000 series |
Zinc |
Very high strength potential |
Aerospace, high-load parts, tooling, and performance components |
6061 Aluminum: The Common CNC Machining Choice
6061 aluminum is one of the most common materials for CNC machined aluminum parts. It offers a practical balance of strength, corrosion resistance, cost, availability, and machinability. It is often used for brackets, plates, housings, fixtures, covers, adapters, frames, and prototype components.
For buyers who are unsure which aluminum grade to start with, 6061-T6 is often a sensible baseline. It is not the strongest aluminum alloy, but it is versatile and widely available. It also responds well to anodizing, which helps when both appearance and corrosion resistance matter.
7075 Aluminum: Higher Strength for Demanding Parts
7075 aluminum is often selected when higher strength is required. It is common in aerospace, robotics, tooling, cycling components, and performance parts where weight reduction matters but the part still needs strong mechanical properties. The tradeoff is that 7075 is generally more expensive than 6061 and can be less corrosion resistant unless properly protected.
For CNC machining, 7075 can produce excellent parts, but material sourcing, tool selection, and finishing expectations should be reviewed carefully. If anodizing, appearance, or corrosion exposure is important, the alloy and temper should be confirmed before production.
Aluminum vs Steel
Aluminum and steel are both metals, but they are not interchangeable. Steel is much denser and usually stronger and stiffer by volume. Aluminum is much lighter and often easier to machine quickly. The right choice depends on strength, weight, stiffness, corrosion, magnetic behavior, cost, surface finish, and operating environment.
| Comparison Point |
Aluminum |
Steel |
| Weight |
Low density, excellent for lightweight parts |
Much heavier |
| Strength |
Good strength-to-weight ratio, alloy dependent |
Usually higher absolute strength and stiffness |
| Corrosion |
Naturally corrosion resistant; anodizing improves protection |
Can rust unless stainless, coated, plated, or treated |
| Machining |
Often faster cutting and good surface finish |
Can be slower, harder, and more tool-wearing depending on grade |
| Magnetism |
Non-magnetic in normal use |
Many steels are magnetic |
| Cost behavior |
Material may cost more per kg, but machining can be efficient |
Material can be cheaper, but machining and finishing vary |
Why Aluminum Is Popular for CNC Machining
Aluminum is popular for CNC machining because it combines useful mechanical performance with efficient manufacturing. Many aluminum alloys cut cleanly, allow high spindle speeds, and produce accurate features with good surface finish. This can reduce machining time compared with harder metals.
- It is light enough for moving assemblies, robotic systems, drones, aerospace brackets, and portable devices.
- It can be machined into plates, housings, heat sinks, manifolds, brackets, covers, adapters, and fixtures.
- It supports many surface finishes, including clear anodizing, color anodizing, hard anodizing, bead blasting, polishing, and plating.
- It is widely stocked in plate, bar, extrusion, and billet forms, which helps control lead time.
- It offers a strong balance between prototype speed and production reliability.
CNC Design Notes for Aluminum Parts
Aluminum is forgiving compared with many engineering metals, but design choices still affect cost, accuracy, and quality. Deep pockets, thin walls, tight internal radii, very small tapped holes, cosmetic surfaces, and tight flatness requirements should be reviewed before manufacturing.
| Design Area |
Recommendation |
Why It Helps |
| Internal corners |
Use the largest practical corner radius. |
Larger tools cut faster and reduce tool chatter. |
| Thin walls |
Avoid overly thin unsupported walls when possible. |
Thin aluminum walls can vibrate or deform during machining. |
| Deep pockets |
Reduce depth or increase tool access where possible. |
Deep features increase cycle time and tool deflection risk. |
| Tapped holes |
Specify thread size, depth, and required engagement clearly. |
This avoids confusion during drilling and tapping. |
| Tolerances |
Apply tight tolerances only to functional features. |
Unnecessary tight tolerances increase cost and inspection time. |
| Cosmetic areas |
Mark visible surfaces on the drawing. |
The shop can protect or finish the correct faces. |
Surface Finishes for Aluminum
One reason aluminum is so widely used is its compatibility with many finishing methods. Clear anodizing can protect the surface while keeping a natural metallic look. Color anodizing adds appearance and identification value. Hard anodizing improves wear and corrosion resistance for demanding parts. Polishing and bead blasting can change the texture and reflectivity.
Finish choice should be discussed early because it can affect dimensions, color consistency, masking, electrical conductivity, and final inspection. For more options, see MTSPi’s surface treatment resources.
Common Applications of Aluminum
Aluminum appears across many industries because it is light, machinable, corrosion resistant, and visually clean after finishing. It is common in aerospace parts, automotive components, automation fixtures, robotics frames, electronic housings, heat sinks, medical device prototypes, optical mounts, consumer hardware, and custom industrial components.
- Aerospace: brackets, plates, housings, lightweight structural components, and test fixtures.
- Automation and robotics: arms, mounts, grippers, frames, sensor brackets, and end-effectors.
- Electronics: heat sinks, enclosures, covers, EMI-related housings, and connector parts.
- Automotive: prototype brackets, battery-related housings, adapters, and performance components.
- Medical and instruments: lightweight fixtures, housings, trays, and development prototypes.
How to Choose the Right Aluminum Grade
When reading a material callout, distinguish the Al element symbol from alloy and temper codes: the symbol alone does not specify the grade or its condition.
Do not choose aluminum only because it is light. Choose the grade based on the actual function of the part. If the part is a general machined bracket, 6061 may be enough. If the part is high-load and weight-sensitive, 7075 may be worth considering. If corrosion, welding, forming, conductivity, or cosmetic anodizing matters, the alloy choice may change.
| Need |
Likely Starting Point |
Important Check |
| General CNC machined parts |
6061-T6 |
Tolerance, finish, and cost target |
| Higher strength lightweight parts |
7075-T6 |
Corrosion protection and material cost |
| Good forming or sheet applications |
3000 or 5000 series |
Bend radius, temper, and surface finish |
| Marine or corrosion exposure |
5000 series or protected 6000 series |
Environment and coating requirements |
| Electrical or thermal conductivity |
1000 series or suitable conductive alloy |
Strength and conductivity balance |
Is Aluminum Better Than Plastic for CNC Parts?
Aluminum is not always better than plastic. It is better when the part needs metallic strength, heat transfer, threaded features, stiffness, surface finish options, or electrical conductivity. Engineering plastics may be better when the part needs chemical resistance, electrical insulation, low friction, transparency, or lower weight without conductive behavior.
If you are comparing aluminum with plastic for CNC machining, review CNC plastic machining and CNC machining materials before locking the drawing. Material selection is one of the easiest ways to control part cost and performance before production begins.
Conclusion
Aluminum is definitely a metal, but its real value comes from the way it balances low weight, machinability, corrosion resistance, conductivity, surface finish options, and alloy flexibility. For many CNC machined parts, aluminum provides a practical middle ground between heavy structural metals and lower-strength plastics.
For a custom aluminum part, send MTSPi your 3D model, drawing, quantity, finish requirement, tolerance notes, and target application. Our team can help review material choice, manufacturability, surface treatment, and inspection through our quote and engineering support process.
FAQ
Is aluminum a metal or nonmetal?
Aluminum is a metal. It has metallic luster, conductivity, ductility, and the ability to form useful engineering alloys.
Is aluminum a ferrous metal?
No. Aluminum is a non-ferrous metal because it is not based on iron. This is why it does not rust like ordinary carbon steel and is not magnetic in normal use.
Is aluminum naturally corrosion resistant?
Yes. Aluminum forms a thin oxide layer that helps protect the surface. In tougher environments, anodizing, coating, or plating can improve protection.
What aluminum grade is best for CNC machining?
6061-T6 is one of the most common starting choices because it is available, machinable, reasonably strong, and suitable for many finishes. 7075 is used when higher strength is needed.
Can aluminum be anodized after CNC machining?
Yes. Many CNC machined aluminum parts are anodized after machining. Clear, color, and hard anodizing are common options depending on appearance, corrosion resistance, and wear requirements.
Is aluminum lighter than steel?
Yes. Aluminum is much lighter than steel. This makes it valuable for aerospace, robotics, vehicles, fixtures, and any assembly where reduced moving mass matters.
Does aluminum rust?
Aluminum does not rust like iron or carbon steel because rust is iron oxide. Aluminum can corrode, but its oxide layer usually provides useful protection.
