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MIL-A-8625 (Anodize)

MIL-A-8625 is the military specification for anodic coatings on aluminum and aluminum alloys, defining Type I (chromic acid), Type II (sulfuric acid), and Type III (hard anodize) coatings.

Type II (sulfuric acid anodize) is the most common aerospace anodize, providing corrosion protection and paint adhesion. It produces a coating typically 5-25 micrometers thick. Class 1 is non-dyed, Class 2 is dyed. Type III (hard anodize) produces a much thicker, harder coating (25-100+ micrometers) for wear resistance, at 2-3x the cost of Type II.

The drawing specifies the anodize type, class, and any color requirements. The anodize vendor must be NADCAP accredited for chemical processing, with the specific MIL-A-8625 type in their scope. The vendor's process batch report is documented on Form 2.

Surface roughness requirements typically apply before anodizing, not after. Anodize changes the surface texture. Measure Ra before sending parts to the anodize vendor.

Related Guides

Anodize Type 2 vs Type 3 NADCAP Requirements

Frequently Asked Questions

What is the difference between Type II and Type III anodize?
Type II (sulfuric acid) is standard corrosion protection, 5-25 micrometers thick. Type III (hard anodize) is a wear-resistant coating, 25-100+ micrometers thick, at 2-3x the cost.

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