Anodizing Standards: MIL-A-8625 Type II and Type III
Quick-reference tables for the two anodize classes KGL runs, with the drawing callout convention, sealing and batch verification we apply.
MIL-A-8625 Classes at a Glance
| Type / Class | Common name | Thickness | Color | Use |
|---|---|---|---|---|
| Type II Class 1 | Decorative, undyed | 8 to 15 μm | Clear | Cosmetic housings, corrosion barrier |
| Type II Class 2 | Decorative, dyed | 8 to 15 μm | Black and colors | Consumer and device parts |
| Type III Class 1 | Hard coat, undyed | 25 to 50 μm | Natural gray | Wear surfaces, tooling |
| Type III Class 2 | Hard coat, dyed | 25 to 50 μm | Jet black | Wear plus appearance |
Related detail specifications seen on drawings: AMS 2471 (anodic treatment of aluminum alloys, low stress), AMS 2468 (hard anodic treatment). Dimensional convention on the drawings we process: specified dimensions apply after anodizing, and features marked with an asterisk are masked during the process.
Verification KGL Applies Per Batch
- Coating thickness by eddy current on witness coupons run with the load
- Sealing quality check on dyed parts (dye stain or weight loss method)
- Post-coat dimensions on critical features, CMM verified, reported
- Appearance against the agreed face map; batch color consistency
- Certificate and RoHS / REACH statements in the shipment package
Corrosion performance is validated by salt spray on request. For conductive or grounding faces, masking keeps metal bare, or a conversion-compatible plating route is discussed instead of anodize.
Anodizing Standards FAQ
What is the difference between Type II and Type III?
Type II is a decorative and corrosion layer, 8 to 15 micrometers, dyed clear or black. Type III hard coat is thicker and much harder, 25 to 50 micrometers, applied cold for wear surfaces. Type III is usually left natural or jet black, and edge sharpness increases with thickness.
Which standard do I put on the drawing?
MIL-A-8625 with type and class: for example Type II Class 2 black, or Type III Class 1. Drawings from aerospace customers also call AMS 2471 for Type II details and AMS 2468 for hard coat. If only a color and thickness are given, we map it to the standard and confirm in the quote.
How is coating thickness measured?
Eddy current per batch on coupon or part, with witness coupons run with the load. Where a dimension matters, we measure before and after on the CMM and report the growth actually seen on your features.
What is sealing and why does it matter?
Fresh anodic oxide is porous; sealing in hot deionized water or nickel acetate closes the pores, locks in dye and improves corrosion resistance. Unsealed coatings can show dye bleed and fail salt spray, so sealing is part of the process, not an option.
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