# Hardcoat Anodizing Type III

> Wear armor for aluminum: an oxide layer as hard as tool steel.

- Process group: Anodizing
- HTML page: https://fabvector.com/finishes/hardcoat-anodizing-type-iii (Portuguese: https://fabvector.com/pt/finishes/hardcoat-anodizing-type-iii)

## Specifications

| Spec | Value |
|---|---|
| Coating thickness | 25–75 µm |
| Tolerance impact | Grows ~50% of coating thickness per surface — at 50 µm that is ~25 µm per face, ~50 µm on a diameter. Pre-finish compensation is mandatory; tolerances tighter than ±0.01 mm post-coat may need grind-after-coat. Threads are normally masked. |
| Corrosion rating | 1,000+ h salt spray typical when sealed — well beyond the 336 h MIL-A-8625 requires for sealed Type III coatings. |
| Appearance | Matte gray to bronze-black depending on alloy and thickness; dye options limited and muted — this is an engineering finish, not a cosmetic one. |
| Applicable substrates | aluminum |

## Not suitable for

Thin-walled parts with sharp corners (coating stress causes micro-cracking at edges); surfaces that must remain electrically conductive afterwards; fits with less than 25 µm of clearance that were not pre-compensated for coating growth; decorative parts expecting vivid color.

## Conditional compatibility

- **aluminum-2024**: High-copper alloy degrades hardcoat quality — coating is softer, less uniform and prone to burning; review with engineering before specifying.

## Typical applications

- Pneumatic and hydraulic cylinder bores
- Slides, guide rails and cam tracks
- Robot joint wear surfaces
- Defense and firearm components