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Surface finishes

Aluminum anodizing services

We offer anodizing type II and III, which are ideal surface finishes for aluminum parts. Anodizing strengthens aluminum parts and is available in several colors, depending on the type. All types of anodizing will increase the lead time and cost per part.

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Anodizing type II

Surface preparation Colors Glossiness Cosmetic availability Thickness** Visual appearance
As machined (Ra 3.2μm / Ra 126μin) Clear, Black, Red, Blue, Orange, Gold Glossy (Above 20 GU) No for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”) Parts are anodized directly after machining. Machining marks will be visible.
Bead blasted Clear, Black, Red, Blue, Orange, Gold Matte (Below 10 GU) Cosmetic on request for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”) Grainy texture, matte finish
Bead blasted Clear, Black, Red, Blue, Orange, Gold Glossy (Above 20 GU) Cosmetic on request for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”) Grainy texture, glossy finish
Brushing(Ra 1.2μm / Ra 47μin) Clear, Black, Red, Blue, Orange, Gold Glossy (Above 20 GU) Cosmetic on request for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”) Parts are manually brushed to reduce marks, then anodized. Brushing lines will be visible.
Tolerances for all surface preparations are held after anodizing

Anodizing type III

Surface preparation Colors Cosmetic availability Thickness Visual appearance
As machined (Ra 3.2μm / Ra 126μin) Black, Natural (thicker layers will appear darker) No 35 to 50μm(0.0013” to 0.0019”) Parts are anodized directly after machining. Machining marks will be visible.
Bead blasted (Glass beads #120) Black, Natural (thicker layers will appear darker) Cosmetic on request 35 to 50μm(0.0013” to 0.0019”) Can be slightly visible if parts are “Not Cosmetic” Completely removed if parts are “Cosmetic”
Non standard requests

* We supply a range of standard colors (see color options). If you need a particular RAL or Pantone color code, please contact networksales@protolabs.com

**As a standard, our anodizing thickness will follow ISO 7599: ISO class AA10 (for clear) and ISO class AA15. If your parts require different standards, please contact networksales@protolabs.com

Color options for aluminum anodizing type II

Color anodizing can have some variation in color due to standard alloy tolerance variations. Check the color scheme below to see the color range.

Black (Black MLW)
Similar to: RAL 9004, Pantone Black 6
Clear
Similar to: depends on material
Sample part showcasing red anodizing
Red (Red ML)
Similar to: RAL 3031, Pantone 1805
Sample part showcasing blue anodizing
Blue (Blue 2LW)
Similar to: RAL 5015, Pantone 3015
Sample part showcasing orange anodizing
Orange (Orange RL)
Similar to: RAL 1037, Pantone 715
Sample part showcasing gold anodizing
Gold (Gold 4N)
Similar to: RAL 1012, Pantone 612

Color options for aluminum anodizing type III

Sample part showcasing aluminum anodizing type III in black color
Black
Sample part showcasing aluminum anodizing type III in natural color
Natural
(thicker layers will appear darker)

Example of an anodized part

Bead blasted + Anodized type II (Matte)
As machined (Ra 3.2μm)

Design considerations for aluminum anodizing

  • Anodizing involves suspending parts via a “jig” or “rack.” This will leave marks on your part where anodizing wasn’t possible. If there are areas on which you can’t accept “jig” marks, please remember to include a technical drawing indicating these areas and follow our cosmetic procedure. Learn more about this on our surface finishing page
  • Anodizing insulates your parts, reducing their conductivity.
  • Masking is not required by default, as anodizing doesn’t raise the thickness of your part significantly. Remember to indicate in your CAD file whether you want specific part areas to be masked or plugged.
  • Type III anodizing, in contrast, adds substantial thickness to your part’s surface. We recommend plugging and masking threaded/reamed holes or other critical-to-function surfaces.

Our anodizing process

Anodizing is an electrolytic process both for protecting aluminum parts against wear and corrosion and for improving cosmetic appearances. Let’s break down the basic steps for anodizing a part:

  • Connect the part to an anode

  • Submerge the part in acidic electrolyte solution

  • Apply a cathode to a metal electrode in the solution

  • Positive ions react with negative O2 ions and the surface becomes porous

  • This grows a layer of aluminum oxide on the part

  • Use corrosion inhibitors or colored dyes for cosmetic purposes

  • Seal the nanopores

Read more about anodizing

Aluminum anodizing video resources

When to (not) Use Anodizing for Your Parts
When to (not) Use Anodizing for Your Parts
Anodizing - What is it and How Does it Work? Complete Aluminium Anodizing Process Explained
Anodizing - What is it and How Does it Work?

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