Surface Finishing

Hard Anodizing (Type III Hardcoat)

Type III hardcoat anodizing is a low-temperature, higher-current-density sulfuric acid anodize that builds a thick, dense oxide layer on aluminum. It is used where wear, abrasion, or electrical insulation matter more than bright color.

Specification

Typical options

Attribute	Typical range	Notes
Coating thickness	~25–75 µm (0.001–0.003 in); ~50 µm common	About 50% builds up, 50% penetrates
Surface hardness	~60–70 HRC equivalent (alloy dependent)	Much harder than base aluminum
Color	Natural gray to bronze; black dye common	Bright dyed colors are limited
Common spec	MIL-PRF-8625 Type III, Class 1 or 2	State class and thickness on drawing

Typical industry ranges for reference. Final thickness, color, and specification are confirmed on your quote and drawing.

Design Tips

What to specify on your drawing

Dimensional allowance

Account for buildup on fits and threads, or mask critical features.

Sharp edges

Add edge radii; coating thins and can craze on sharp edges.

Alloy

6061 and 7075 hardcoat well; high-copper 2024 and cast alloys give thinner, darker results.

Sealing

Sealing improves corrosion resistance but can slightly reduce wear resistance; specify if needed.

Compatible Materials

Materials often paired with this finish

Aluminum 6061

Common material for this finish.

Aluminum 7075

Common material for this finish.

Aluminum 2024

Common material for this finish.

Surface Finishing Service

See all finishing and post-processing options.

Add a Finish

Include finish requirements with your RFQ.

Note the finish, specification, color, thickness, and masked areas on your drawing so the quote reflects them.

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