Aluminum is the most widely specified metal for CNC-machined parts. Its combination of low density (2.70–2.82 g/cm³), tensile strength up to 575 MPa in high-strength alloys, excellent machinability, and broad surface finish compatibility — including anodizing, hard coat, and powder coating — makes it the default choice across aerospace, automotive, electronics, and general industrial applications.
Three decisions determine whether a CNC-machined aluminum part performs and costs correctly in service: alloy selection (6061, 7075, 5083, and 2024 are not interchangeable and differ substantially in strength, corrosion resistance, and machinability), temper condition (T6, T651, and T7351 each produce different mechanical properties from the same base alloy), and surface finish sequencing (anodizing adds measurable thickness that must be accounted for in tight-tolerance features). All three are covered below.
At a Glance
| Field | Value |
|---|---|
| Available alloys | 2014, 2014-T6, 2017A, 2024-T351, 5052, 5052-H32, 5083-H111, 5083-H32, 6061, 6061-T6, 6061-T651, 6063, 6063-T5, 6063-T6, 6082, 6082-T6, 6082-T651, 7050, 7075-T6, 7075-T651, 7075-T7351, MIC6 |
| Standard tolerance | ±0.125 mm |
| Precision tolerance | ±0.025 mm (alloy and feature dependent) |
| Min wall thickness | 0.8 mm |
| Max part size (milling) | 600 × 300 × 200 mm |
| Max part size (turning) | 500(Dia) × 4000(L) mm |
| Lead time | 1–5 Days |
| Certifications | ISO 9001:2015 · AS9100D · ISO 13485:2016 |
Why Aluminum Is Used for CNC-Machined Parts
Aluminum machines 3–5× faster than most steels, directly reducing cycle time and per-part cost. Sharp carbide tooling, high spindle speeds, and standard flood or air-blast cooling are sufficient across all common alloys — no specialist process controls are needed. This machinability advantage, combined with a strength-to-weight ratio that outperforms steel on a per-kilogram basis for most structural applications, makes aluminum the default metal for CNC-machined parts where weight, lead time, or finish quality matter.
The properties that drive alloy selection:
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Strength— ranges from 130 MPa (6063-T5) to 575 MPa (7075-T6). Match the alloy to the actual load case — over-specifying a high-strength alloy adds cost without benefit.
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Corrosion resistance— 5xxx and 6xxx series have good natural corrosion resistance. 2xxx and 7xxx series are susceptible — parts in exposed environments require anodizing or chemical film coating.
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Machinability— 6061 and 6082 machine easily with excellent surface finish. 2024 and 7075 require sharper tooling and reduced feed rates.
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Weldability— 5xxx and 6xxx series are weldable. 2xxx and 7xxx have poor weldability — design for mechanical fastening if joining is required.
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Finish compatibility— all alloys anodize, but 2xxx series produces inconsistent colour due to copper content. Specify 6xxx series for cosmetic anodizing.
Aluminum Alloys for CNC Machining
Aluminum alloys are grouped into series by primary alloying element. Understanding which series an alloy belongs to tells you immediately about its corrosion resistance, weldability, and finish behaviour — before reading a single data point.
All values are indicative reference ranges for engineering-grade stock. Confirm against the specific supplier datasheet before finalising structural calculations.
2xxx Series — High Strength, Aerospace Grade
Primary alloying element: copper. Highest strength in the aluminum family, excellent fatigue resistance. Poor corrosion resistance without surface treatment — plan for anodizing or Alodine. Poor weldability — design for mechanical fastening. Not recommended for cosmetic anodizing due to uneven colour from copper content. Maximum continuous service temperature is approximately 125°C for 2024-T351 before significant strength loss occurs.
| Material | Density (g/cm³) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (HBW) | Fatigue Strength (MPa) |
|---|---|---|---|---|---|---|
| Aluminum 2014 | 2.78–2.82 | 100–430 | 190–490 | 6–18 | 45–140 | 90–140 |
| Aluminum 2014-T6 | 2.80–3.0 | 400–430 | 460–500 | 7–13 | 130–150 | 120–140 |
| Aluminum 2017A | 2.75–2.80 | 110–280 | 200–420 | 6–18 | 55–120 | 90–130 |
| Aluminum 2024-T351 | 2.72–2.80 | 320–340 | 450–480 | 10–19 | 120–145 | 100–140 |
Specify 2xxx when:maximum strength-to-weight ratio or fatigue resistance is required — aerospace structural components, high-cycle mechanical parts, and load-bearing assemblies.
5xxx Series — Marine and Corrosion Resistant
Primary alloying element: magnesium. Non-heat-treatable (strain-hardened). Excellent corrosion resistance including saltwater and marine environments. Good weldability. Lower strength than 6xxx and 7xxx series. 5xxx alloys retain good mechanical properties up to approximately 65–120°C; they are not suited to sustained elevated-temperature structural use.
| Material | Density (g/cm³) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (HBW) | Fatigue Strength (MPa) |
|---|---|---|---|---|---|---|
| Aluminum 5052 | 2.66–2.70 | 90–220 | 190–280 | 10–22 | 46–70 | 100–130 |
| Aluminum 5052-H32 | 2.65–2.70 | 170–200 | 210–260 | 10–20 | 55–65 | 110–125 |
| Aluminum 5083-H111 | 2.66–2.78 | 125–165 | 210–300 | 10–15 | 60–80 | 120–150 |
| Aluminum 5083-H32 | 2.65–2.70 | 230–260 | 310–340 | 9–15 | 80–95 | 110–170 |
Specify 5xxx when:the part operates in marine, chemical, or high-humidity environments. 5083 is the standard for marine structural components and pressure vessels. 5052 for chemical tanks, architectural hardware, and formed sheet components.
6xxx Series — General Purpose (Most Widely Specified)
Primary alloying elements: magnesium and silicon. Heat-treatable. Best balance of strength, machinability, corrosion resistance, weldability, and anodize quality across all aluminum alloys.6061-T6 is the most commonly specified aluminum alloy for CNC machining globally.6082 is the European equivalent and the preferred choice for UK and EU supply chains. 6061-T6 and 6082-T6 retain useful strength up to approximately 150°C; above this threshold, temper strength degrades progressively.
| Material | Density (g/cm³) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (HBW) | Fatigue Strength (MPa) |
|---|---|---|---|---|---|---|
| Aluminum 6061 | ~2.70 | 240–280 | 290–320 | 10–15 | 90–100 | 90–120 |
| Aluminum 6061-T6 | ~2.70 | 240–280 | 290–320 | 8–14 | 90–100 | 90–110 |
| Aluminum 6061-T651 | 2.70–2.71 | 240–280 | 270–320 | 10–17 | 90–100 | 95–110 |
| Aluminum 6063 | ~2.70 | 90–130 | 130–180 | 8–18 | 40–60 | 55–80 |
| Aluminum 6063-T5 | ~2.70 | 140–150 | 180–190 | 10–15 | 55–70 | 65–75 |
| Aluminum 6063-T6 | ~2.70 | 160–215 | 190–245 | 8–12 | 70–80 | 65–75 |
| Aluminum 6082 | 2.70–2.71 | 240–280 | 290–340 | 8–15 | 90–100 | 80–120 |
| Aluminum 6082-T6 | ~2.70 | 250–280 | 295–340 | 8–12 | 90–105 | 90–130 |
| Aluminum 6082-T651 | 2.70–2.71 | 260–310 | 300–340 | 8–12 | 89–95 | 90–120 |
Specify 6061-T6 or 6082-T6 as the defaultfor structural brackets, housings, frames, fixtures, and general mechanical components. Specify 6063 for architectural and cosmetic applications requiring consistent anodize quality.
7xxx Series — Highest Strength
Primary alloying element: zinc. Heat-treatable. Highest tensile strength of all aluminum alloys — approaches mild steel. Poor weldability. 7075-T6 is susceptible to stress corrosion cracking (SCC) in corrosive environments — specify 7075-T7351 where SCC resistance is required. T7351 sacrifices approximately 15% strength vs T6 but is significantly more reliable in exposed or humid service conditions. 7075-T6 loses significant strength above approximately 120°C — for applications with sustained elevated temperatures, specify 2024-T351 or move to titanium.
| Material | Density (g/cm³) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (HBW) | Fatigue Strength (MPa) |
|---|---|---|---|---|---|---|
| Aluminum 7050 | 2.70–2.80 | 390–500 | 490–570 | 8–12 | 130–150 | 150–230 |
| Aluminum 7075-T6 | 2.80–2.82 | 480–505 | 540–575 | 7–11 | 140–160 | 150–170 |
| Aluminum 7075-T651 | 2.70–2.85 | 480–505 | 540–570 | 8–12 | 140–160 | 150–170 |
| Aluminum 7075-T7351 | 2.80–2.82 | 410–440 | 500–530 | 7–12 | 130–150 | 150–170 |
Specify 7075-T6for maximum strength-to-weight ratio in non-welded, low-corrosion-risk applications.Specify 7075-T7351where stress corrosion cracking resistance is required.Specify 7050for thick-section aerospace plate where through-thickness toughness and resistance to exfoliation corrosion are priorities.
MIC6 — Precision Tooling and Jig Plate
Cast aluminum tooling plate with controlled flatness, tight thickness tolerances, and a stress-free microstructure. Maintains flatness directly off the machine without stress-relief operations. Lower tensile strength than wrought alloys — not suitable for structural load-bearing applications. The standard choice wherever dimensional stability and flatness are more important than strength. MIC6 is specified solely for ambient-temperature tooling, fixturing, and precision reference applications — it is not intended for elevated-temperature service.
| Material | Density (g/cm³) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (HBW) | Fatigue Strength (MPa) |
|---|---|---|---|---|---|---|
| Aluminum MIC6 | ~2.70 | 100–110 | 160–170 | ~3 | 65 | 50–60 |
Specify MIC6 when:the part is a tooling plate, fixture base, vacuum chuck, or precision reference surface where flatness and stability take priority over strength.
Not sure which alloy to specify?Upload your drawing and our engineering team will confirm alloy selection, temper, tolerances, and finish options.
Quick Alloy Selection Guide
Use the three steps below to move from application requirement to a shortlisted alloy. All property data is in the series tables above.
Step 1 — Start from your design priority
| Design priority | Start with |
|---|---|
| General structural parts, brackets, housings, fixtures | 6061‑T6 / 6082‑T6 |
| Maximum strength‑to‑weight, non‑welded, low corrosion risk | 7075‑T6 / 7075‑T651 |
| SCC resistance or thick‑section aerospace plate | 7075‑T7351 / 7050 |
| Marine, chemical, or high‑humidity environment | 5083‑H111 / 5052 |
| Tooling plates, fixture bases, precision reference surfaces | MIC6 |
| Cosmetic anodizing, architectural, or consistent colour finish | 6063‑T5 / 6063‑T6 |
Step 2 — Check the columns that matter for your load case
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Yield and tensile strength— for load‑bearing capacity and safety margins.
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Elongation at break— for ductility where forming, impact, or energy absorption is involved.
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Fatigue strength— for high‑cycle or vibrating parts (actuators, rotating components, engine brackets).
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Hardness (HBW)— as a proxy for wear resistance and surface durability.
Step 3 — Confirm process and finish compatibility
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Welded joins required → stay within 5xxx or 6xxx series.
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Cosmetic anodizing required → favour 6xxx, especially 6063 and 6061.
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Corrosive or outdoor service without surface treatment → 5xxx series only.
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Stress corrosion risk in high‑strength application → 7075‑T7351 over 7075‑T6.
If two alloys still appear equivalent after this pass, upload your drawing with a note on operating environment and load case. Our engineers will confirm the alloy, temper, and finish specification before you freeze the design.
Design Considerations for Aluminum Parts
Use the following values as general design guidelines for CNC‑machined aluminum parts. Actual limits depend on alloy, part size, fixturing, and tooling. For designs that need to push beyond these ranges, Clarwe can review your CAD data and advise on achievable tolerances and potential design adjustments.
| Design aspect | Recommended guideline for aluminum CNC parts |
|---|---|
| Minimum wall thickness (standard) | ≈ 0.8 – 1.0 mm for most walls |
| Minimum wall thickness (feasible) | Down to ≈ 0.5 mm in localized areas |
| Maximum wall height‑to‑thickness ratio | Aim for ≤ 8:1 where possible |
| Minimum internal corner fillet radius | ≥ 0.5 – 1.0 mm in shallow pockets |
| Deep pocket fillet radius | At least 1/3 of pocket depth as a starting point |
| Practical minimum hole diameter (standard) | ≈ 2.5 mm |
| Practical minimum hole diameter (feasible) | Down to ≈ 1.0 mm with appropriate tooling |
| Threaded hole size | Prefer M3 and larger for most designs |
| Distribution of tight tolerances | Apply tight tolerances only to critical features |
Cost-Saving Design Tips for Aluminum CNC Parts
Small design decisions have a direct impact on machining time and per-part cost. The following practices reduce cost without compromising function:
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Apply tight tolerances selectively.Specify ±0.025 mm only on functional mating features — bores, pins, and critical interfaces. Applying precision tolerances across the whole drawing increases inspection time and cost without engineering benefit.
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Keep pocket depth-to-width ratios within 4:1.Deeper narrow pockets require longer, more flexible tooling, slower feed rates, and additional finishing passes. Where depth exceeds 4× width, consider step-drilling or design review before committing.
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Consolidate features to one or two setups.Each additional machine setup adds fixture time and potential datum error. Where possible, design features to be accessed from the same orientation.
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Default to 6061-T6 or 6082-T6 for prototypes.Move to 7075 only when load analysis confirms it is necessary — 7075 stock costs more, machines slightly slower, and requires surface treatment in corrosive environments.
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Specify minimum thread engagement correctly.For aluminum, a thread engagement length of 1.5× to 2× the nominal thread diameter is the standard recommendation. Over-specifying thread depth in thin walls creates tool breakage risk.
Surface Finish Compatibility
Aluminum is compatible with a wider range of surface treatments than most metals, which is one of the primary reasons it is so widely specified for CNC-machined parts. Available finishes at Clarwe include:
As-machined
No secondary treatment. Ra 1.6–3.2 µm typical. Suitable for internal components, structural brackets, and non-cosmetic parts where dimensional precision matters more than appearance.
Bead blast
Uniform matte texture across all external surfaces. Removes tool marks and prepares the surface for anodizing. Commonly specified before Type II anodizing for cosmetic parts.
Type II anodizing (sulfuric acid)
Builds 5–25 µm per surface. Improves corrosion resistance and allows clear or colour dyeing. The standard cosmetic and protective finish for 6061, 6082, and 6063 alloys. Specify 6xxx series alloys for consistent, colour-accurate results — 2xxx series produces uneven colour due to copper content.
Type III hard anodize (hardcoat)
Builds 25–100 µm per surface. Significantly increases surface hardness and abrasion resistance. Specified for wear surfaces, sliding interfaces, valve bodies, and aerospace structural components. Note: hard anodize adds measurable dimensional growth — critical fits and threaded features should be masked or pre-compensated on the drawing.
Chemical conversion coating (Alodine / Chromate)
Thin, electrically conductive protective layer. Used where conductivity must be preserved — RF housings, EMI shielding components, and grounded assemblies. Can be clear or gold in colour.
Powder coating
Colour-critical and brand-driven exterior applications. Adds 60–120 µm. Specify masking requirements for threaded inserts and precision mating faces on your drawing.
Electroless nickel plating (ENP)
Uniform deposit including internal bores and complex geometry. Used where wear resistance and corrosion resistance are both required without sacrificing dimensional predictability.
When planning any surface finish, define critical dimensions on the drawing with the finishing sequence in mind. Anodizing and plating add measurable thickness — interference fits, bore diameters, and threaded regions must account for this before machining.View all surface finish options →
Industries and Applications
Aluminum CNC-machined parts are used across most engineering sectors. The same properties that make aluminum easy to machine — low density, predictable cutting behaviour, and broad finish compatibility — also make it suitable across a wide
range of service environments, from aerospace structural components to precision laboratory fixtures.
Aerospace and Defense
Aluminum 2024-T351 and 7075-T6 are the primary structural alloys for flight hardware. Typical parts include wing ribs, bulkheads, seat rails, control surface brackets, and avionics housings. 7075-T6 is specified for maximum strength-to-weight ratio in load-bearing, non-welded applications. Where stress corrosion cracking is a risk — particularly in thick sections or humid service environments — 7075-T7351 is the correct specification, trading approximately 15% tensile strength for significantly improved SCC resistance. Clarwe holds AS9100D certification for aerospace production.
Automotive and Motorsport
6061-T6 and 7075-T6 are standard for suspension components, gearbox housings, valve bodies, pedal assemblies, and lightweight structural brackets. Motorsport applications frequently specify 7075-T6 for maximum weight reduction under high
mechanical load. 6061-T6 is the default for general powertrain and chassis structural components where weldability is also a requirement. Tight tolerances on bore features, mounting faces, and threaded inserts are routinely held to ±0.025 mm.
Electronics and Enclosures
6061-T6 and 6063-T6 are the dominant alloys for electronic enclosures, RF shielding housings, heat sinks, chassis panels, and instrument frames. 6063 is preferred wherever consistent cosmetic anodizing is critical — its lower copper content produces a more uniform, colour-accurate anodized finish than 6061. Connector cutouts, PCB mounting bosses, and lid mating interfaces are common high-tolerance features in this category.
Marine and Offshore
5083-H111 and 5052 are the standard choices for marine structural and hardware applications. Both alloys provide excellent resistance to saltwater corrosion without surface treatment and are readily weldable — important for structural joins and field repair. 5083 is used for hulls, deck hardware, pressure vessels, and structural frames. 5052 is specified for formed tanks, chemical storage hardware, and architectural fittings in coastal environments.
Medical Devices and Laboratory Equipment
6061-T651 and MIC6 are common in medical device frames, surgical tool components, test fixture bases, and laboratory instrument housings. MIC6 tooling plate is the standard for precision reference surfaces, vacuum chucks, and fixture bases where flatness is required directly off the machine without additional stress-relief operations. Clarwe holds ISO 13485:2016 certification for medical device manufacturing.
Industrial Tooling and Fixtures
MIC6 and 6082-T651 are the standard alloys for jig plates, fixture bases, machine beds, and precision gauging components. MIC6 is specified where flatness and dimensional stability take priority over strength. 6082-T651 is used where higher structural load capacity is also required. Aluminum's machinability advantage — cutting 3–5× faster than most steels — directly reduces tooling and fixture lead times and per-part cost on repeat production runs.
Supplying into a regulated industry? Clarwe holds ISO 9001:2015, AS9100D, and ISO 13485:2016 certification. Upload your drawing and our engineering team will confirm alloy, finish, and documentation requirements before production begins.
Consult Engineering Team →
Frequently Asked Questions
Which aluminum alloy is best for CNC machining?
6061-T6 is the most widely specified aluminum alloy for CNC machining globally. It offers the best overall balance of strength (290–320 MPa tensile), machinability, corrosion resistance, weldability, and anodize quality. For UK and European supply chains, 6082-T6 is the functionally equivalent choice and typically more readily available in metric stock sizes. Specify 7075-T6 only where maximum strength-to-weight ratio is the primary design driver — it machines well but has poor weldability and requires surface treatment in corrosive environments.
What is the difference between 6061-T6 and 6061-T651?
Both designations describe the same base alloy in the same T6 temper condition. The T651 suffix indicates that the plate has been stress-relieved by controlled stretching after solution heat treatment. This reduces residual internal stress in the stock, which matters for precision-machined parts — particularly large components, thin walls, or features with tight flatness requirements, where residual stress can cause distortion during or after machining. For most CNC applications, 6061-T651 plate is the preferred specification over standard 6061-T6 plate.
Does anodizing affect part dimensions?
Yes. Type II (standard) anodizing builds a layer of approximately 5–25 µm per surface. Type III (hard coat) anodizing builds 25–100 µm per surface. The anodic layer grows approximately 50% into the base material and 50% outward, so effective dimensional growth is roughly half the total layer thickness. For tight-tolerance features — interference fits, bore diameters, threaded regions, and precision mating faces — critical dimensions should be defined on the drawing with the anodizing allowance specified, or those features masked during the anodizing process.
Which aluminum alloys can be welded?
5xxx series (5052, 5083) and 6xxx series (6061, 6082) alloys are weldable using standard TIG or MIG processes with appropriate filler rod. 2xxx series (2014, 2024) and 7xxx series (7075, 7050) alloys have poor weldability — the copper and zinc alloying elements cause hot cracking susceptibility during fusion welding. If your design requires welded joins, specify a 5xxx or 6xxx alloy. For 2xxx and 7xxx series parts where joining is unavoidable, design for mechanical fastening.
What tolerances can be held in CNC-machined aluminum?
Standard CNC machining holds ±0.125 mm across general features. Precision tolerances of ±0.025 mm are achievable on critical features with appropriate fixturing, tooling, and inspection — subject to alloy and feature geometry. Minimum wall thickness for standard milling is 0.8 mm; down to 0.5 mm is feasible in localised areas with suitable tooling. For features requiring tolerances tighter than ±0.025 mm, secondary operations such as grinding or honing may be required. Upload your drawing and our engineering team will advise on achievable tolerances for your specific design.
When Aluminum Is a Good Fit — and When Another Material Is Better
Aluminum is the right choice when:
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Part weight must be minimised without moving to titanium or composites — aluminum offers the best cost-per-kilogram strength-to-weight ratio of any common CNC metal.
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Good machinability and short lead times are priorities — aluminum machines 3–5× faster than steel, directly reducing cycle time and cost.
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Corrosion resistance and finish quality matter — 5xxx and 6xxx series alloys have inherent corrosion resistance, and all alloys accept anodizing for additional protection and appearance.
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The application involves prototyping through series production — aluminum is cost-competitive at both low and high volumes.
Another material may be better when:
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Very high surface hardness or abrasion resistance is required without coatings — considerAlloy Steel(4140, 4340) or hardened stainless steel grades.
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Parts must operate at sustained temperatures above 150°C — aluminum loses temper strength progressively above this point; considerTitanium Ti-6Al-4Vor heat-resistant steel grades.
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Maximum corrosion resistance is required without surface treatment in aggressive chemical environments — considerStainless Steel316L.
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Very high rigidity-to-weight is required and weight budget allows — titanium offers higher modulus per kilogram for critical structural applications.
Ready to machine aluminum parts?
Upload your CAD model for an instant quote with alloy, finish, and lead time — or request a DFM review from our engineering team before committing to a specification.